[VẬT LÝ 12] ĐIỆN XOAY CHIỀU - PHƯƠNG PHÁP GIẢN ĐỒ VECTO NỐI TIẾP - THẦY VNA
Oct 11, 2023
Hello everyone, today I'm going to show you a very good way to calculate the electric field with the connected RLC band, which is the connected vector reduction method.
You have learned two methods that I have taught, which are the square method and the central vector reduction method.
Today, you will learn a stronger method, which is the connected vector reduction method.
This is a hidden method, which is an important point in our RLC.
From this method, you will increase the ratio, which is a method that specializes in solving extreme calculations with many corners.
This is the foundation, these are the very important parts.
I will show you the full theory and how to use this method.
After that, we will go to solve the exercises from the most basic to the highest level.
And we will solve the most difficult questions in university exams using this method.
First, let's go to the performance of the connected vector reduction method.
It is still built on the basis of the central vector reduction method or the general vector reduction method.
That is UL up, UR horizontal and UC down.
These are the three most basic principles when you learn the reduction method.
As you can see, the connected vector reduction method is related to the order of the points in the circuit.
For example, you can see that our points in the circuit are in the order of A, M, N, B.
First, the starting point of this circuit is at point A.
After that, you can see that from A to M, it has to go through the loop L.
This is considered a loop.
I will show you with the loop behind.
You can see that from A to M, it has to go through the loop L.
So the vector UL has to be up, right?
The vector UL has to be up.
From A to M, the vector UL has to be up.
You can see that our UAM is UL.
Our UAM is UL.
I don't need to show UL anymore.
After that, you just need to look at UL, UR, and UC.
You can see that from A to M, it has to go through the loop L.
From M to N, it has to go through the loop R.
The vector UR has to be up, right?
Normally, if you draw UR, you will draw it down here to have the same origin as UL.
It is called the origin-aligning method.
Usually, UR is drawn from here to here, right?
UR is horizontal.
But we will do the alignment method here.
The vectors are connected to each other.
The head of this vector is attached to the tail of that vector.
I will draw it for you to imagine it easily.
From M to N, it has to go through the loop UR.
The vector UR is horizontal.
It ends here.
You see?
Normally, I will draw the vector UR down here to have the same origin as UL.
But now I draw it up here.
In mathematics, what is it called?
The forward vector does not change the direction.
I will draw the forward vector up here.
Its direction is still horizontal and its direction is still from left to right.
I just draw it forward so that it connects to each other.
It does not have to have the same origin anymore.
The head of this vector is attached to the tail of that vector.
Is it done?
The electric field is 2 over 3.
A to M, M to N.
In the end, N to B ends this field.
You see?
It goes from N to B through C.
What about our vector UC?
Our vector UC is horizontal.
So the forward vector is horizontal.
But when we draw this vector,
there is a very important thing.
We will draw it down to the extent that it is long or short.
Here I am drawing UC down, shorter than UL.
It's like a saying that I often ask my previous students.
Too much or not too much.
Too much or not too much, what does it mean?
When you draw the last guy, our UC,
this is not too much,
that is, it does not exceed the UL.
What is our field?
Our field is horizontal.
And when you draw UC, it's too much.
Is it right?
Is UC greater than UL?
Our field is horizontal.
So whether it's too much or not here
depends on the calculation.
People give opinions.
And the most difficult question you need to answer
is whether it's too much or not.
Here I am drawing not too much.
That is, it is horizontal.
The point from N to B ends here.
It's just short.
So we have completed our electric field.
That is, A, M, N, B in order.
And the UL principle is up,
UR is horizontal, and UC is down.
Where is the line of electricity Y?
Our vector Y is always horizontal.
And you take it, it has a dot.
Let it be a little different.
Here.
My line of electricity Y is always horizontal.
So where is the whole U?
Now you imagine our whole U is UAB.
Is it right?
My whole U is UAB.
So the whole U is connected from point A to point B.
But point A is on the picture here,
point B is on the picture here, right?
You will connect from A to B
to get the whole U vector.
And of course you can see
this vector is earlier than the line of electricity Y.
Because if you draw UC shorter than UL,
the line is opposite.
So UAB is earlier than Y,
an angle phi that we still often calculate,
according to tan phi and cos phi.
So what do you see?
Normally, you sum the whole UAB vector
according to what method?
Summing vectors according to what principle?
Parallel form, right?
So here I don't draw a parallel form.
I don't have a line at all
in the process of summing vectors.
Why?
Do you remember the 10th grade knowledge?
I explained the principle of calculus.
If you forget, please remember.
Normally, if two vectors have the same origin,
like this.
Is it right?
If I sum the vectors,
I will follow the principle of
parallel form, right?
And it creates two lines like this.
Is it right?
And where do they intersect?
The summing vector is there.
Do you understand?
So you see,
to sum this picture,
I draw 5 lines, right?
It has 2 components.
1 is the sum
and 2 is the intersection
to get the top of the sum.
But you know,
if we use the method of summing vectors,
just like this,
the U is horizontal,
the sum is up here, right?
If we use the method of summing vectors,
for example,
I sum these two vectors, right?
This vector.
The vector below, right?
There.
You will not follow the principle of parallel form
but I sum this vector up here.
Is it right?
Sum it up here.
Is it done?
Then I connect from the top of the first vector
to the top of the second vector.
The origin of the first vector
to the top of the second vector
is the sum of the components.
Is it right?
And let's forget about this.
There.
Because I already summed it up here.
However,
with this drawing style,
I get more advantage.
Here I only draw 3 lines.
There are 2 components
and 1 sum.
This is about 5 lines.
However,
when it comes to the method of summing vectors,
look at this.
It is very neat
because it does not generate many lines
in the process of summing.
We need UAB, right?
Summing from point A to point B
is UAB.
For example,
we need UAN, right?
UAN is summing from A to N
is UAN.
Is it clear?
Here.
Let's take an example.
I sum UAN in.
Is there any problem?
Look at this.
Summing from A to N.
Of course, the vertex must be at point A.
Point A is the origin.
Okay?
According to you,
what is the angle between UAN and UNB?
Listen carefully.
UAN and UNB.
Many of you will get it wrong like this.
AN and NB.
You see it as 2 edges.
This is the joint angle of 2 edges.
I agree.
This is the joint angle of 2 edges.
However,
if the joint angle of 2 vectors
is not the joint angle of 2 vectors,
as you know,
vector AN is summing from point A
and vector NB is summing from point B.
The joint angle is not the joint angle of 2 vectors.
The joint angle of 2 vectors
is the joint angle of 2 edges.
Do you get it?
Therefore,
the joint angle of 2 vectors
must be the same
as the joint angle of 2 edges.
Or the same as the joint angle of 2 edges.
Do you know the direction of this vector?
The direction is here.
The direction of NB is down.
The direction of NA is like this.
The direction of NA is down like this.
The outer angle
is the joint angle of 2 vectors.
Because there are 2 edges
from the point A.
Therefore,
when you define the joint angle of 2 vectors
in this equation,
you must remember
the joint angle of 2 vectors
according to mathematics.
Do you get it?
Do not use the joint angle of 2 edges
which is wrong.
You have to see
the direction of it.
Do you get it?
Then you will know
exactly the joint angle of it.
That's it.
In this way,
if you need U,
you just need to connect 2 points.
For example,
if you need UMB,
you just need to connect M to B.
If you need UAN,
you just need to connect A to N.
You do not need to follow
the general principle of equation.
Do you get it?
If you need U,
you just need to connect 2 points of U.
Do you get it?
Right after this,
I will show you
a more complicated form
which is with an irreducible paper.
Next,
I will show you
a more complicated form.
It is still the form of LRC.
But now,
our string is
waiting for the small r.
That means
we have all
the parts in this array.
You can see
1, 2, 3, 4.
I will have 4 parts in the array
which is equivalent to 4 vectors
that I need to represent.
The principle of this
is that I just follow
the sequence of points in the array.
For example,
the beginning of this array
is point A, right?
I just write point A.
Right?
Dot one,
is it A?
I will show you
step by step.
You are in the 12th grade.
You are not a kid anymore.
You have to write
step by step.
Look at the way I do it.
It is step by step.
Do you get it?
First,
dot point A.
From A to M,
it goes through
how many vectors?
From A to M,
it goes through
2 vectors.
One is L
and the other is R.
The direction of UL is up
and the direction of UR is horizontal.
So,
look at the following.
Many of you
will ask me
that
if L and R are like this,
they are not in the same order.
You can draw any vector first.
Many of you will ask me
whether to draw UL first
or UR first.
It depends on
your math
and your math experience.
Of course,
when you solve a equation,
you only need to draw
one more line,
one more line.
It determines
whether the element
can solve the equation or not.
So,
when you do a lot of things,
you will accumulate a lot of experience
on what you should draw first.
L first
or R first.
Do you understand?
There is no rule
and there is no rule.
It depends on
what you draw first
and what you draw later.
Remember this.
There is no specific method
to draw anything first.
Do you understand?
For this example,
I draw UL first.
Right?
From A to M,
there is UL.
UL is up.
So,
UL is up.
Do you understand?
Let's simplify
the details.
Let's continue.
Have you finished
the point M?
Of course,
you know that
you can't write M here.
From A to M,
there is a small r.
So,
you can't write M here,
but you have to draw
a horizontal line
one more time.
Do you understand?
You have to draw
a horizontal line
one more time.
Ok?
At least.
There.
It's like this.
Then,
what is the point?
Then,
you will finish
the point AM.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
Right?
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
L is up
and R is horizontal.
The point AM
has 2 quadrants.
Done?
Then, from N to B
and go through L and R.
Then, from N to B
and go through L and R.
Right?
What do you draw first?
For this table,
I draw L first
and then R.
But what will you do
for this table?
Just look at this.
If you draw L first,
it will be a bit ugly.
If you draw L first,
it will be a bit ugly.
You just draw M and N vertical.
Now, you draw horizontally.
You just draw horizontally.
It will be disfigured.
In the graph,
it's a bit hard
to draw like that.
It's just for fun.
It's a bit ugly.
So, you have to
It's a bit ugly, so you have the experience that you shouldn't draw L and C on top of each other, it's ugly, right?
So you will come to point N, there are two options to go to point B, go through R first, then go to L.
Draw it apart, don't draw it close to each other, right? Let it expand the picture.
So you will draw a small R lying horizontally, right? Then draw L up.
When you go up, there are two options, too much or not too much, I draw too much to make it beautiful, right?
When you go up, I draw too much to make it beautiful, right?
That's it, this is where we finish point B, right?
Follow the pattern, right? A, M, then B, A, M, N, B, done?
The line N, B is a two-dimensional line, so it's a bit complicated.
Then I will connect from A to B, which is the whole U line.
See? Connecting from A to B is a bit complicated, right? It's the whole U line.
Next, what conditions do people often give in this equation?
You see, I connect from N to B, N to B is a diagonal line, right?
N to B is a diagonal line, there.
A to N is a diagonal line, right?
See?
In this equation, people often give a condition for you to judge whether it is too much or not.
That is the M, B, square root of A, N, right?
For M, B to be square root of A, N, A, N do not tilt down.
So if M, B wants to be square root, M, B has to tilt up, right?
So usually point B has to go over, that is, wait for me to draw too much, see?
So A, N tilts down, so if M, B wants to be square root, M, B has to tilt up like this, right?
And point B has to go up, but if point B is low like this, then M, B is still parallel to A, N, right?
Can't go over, can't be square root.
So I usually use the condition M, B, square root of A, N.
It sounds like that.
M, B, square root of A, N.
It will be too much, right?
Well, this equation is a bit ugly.
Let's go to the obvious example.
Well, many of you will ask, teacher, teacher, the symbol to do the equation of the connected vector,
what is it used for?
To know it is to use the equation of the vector, right?
Well, the common element of the equation of the vector is the equation of having an angle and many angles.
If there is an angle and many angles, then I will use the equation of the vector, right?
I will not use the equation of the square root here.
The square root must have a full equation, right?
Here I will use the equation of the square root because I have two angles, right?
Well, you can see that we can't do the equation of the square root
because there is no R in the middle and there is no triangle, right?
Well, the common method that I often learn later is the connected method, right?
Well, let's start.
The beginning of this line starts from point A.
From A to M, it goes through L and R.
So what do we draw first?
Draw L first to avoid it coincides with C, right?
So I will draw UL up, right?
After that, UR is horizontal, right?
That's it.
This is the end of the line AM, right?
From AM to MN, it goes through C.
And our UC will go down.
Now my direction will be too or not too.
As you can see, this line will be too or not too based on the condition of the beginning of the line.
You know that UC is too or not too, right?
But usually you have to guess.
There are only two situations, so you can draw whatever you like.
Then we will see if the condition is correct or not.
It is said that UAM is diagonal with UMN, the angle is 150 degrees.
So our AM is the connection from A to M.
It is a diagonal line here, right?
AM to MN, our diagonal angle is the outside angle here, right?
And of course, this angle is 150 degrees.
Whether you draw MN or not, this angle is always greater than 90.
But the next condition is the important condition.
That is AN diagonal with MN, right?
Look closely, AN diagonal with MN is 30 degrees.
Where is AN? This is AN.
See? This is AN and this is MN, right?
And our angle is 30 degrees.
Now it's right.
If you draw N up here, right?
If N is here, the angle is 90, guys.
If N is up here, the angle is greater than 90.
So you just try to draw it.
You have to try to draw it, okay?
So you know that this angle can't be 30.
If it's up here, it has to go down.
Done?
Continue from N to B is to go through the R line.
See?
That's it.
Go through the R line.
End here is point B.
And what is the requirement to find U?
The requirement to find UAB is to connect this.
From A to B, right?
That's it.
The requirement to find this green angle.
Which angle do you know?
MN is 100 degrees.
This angle is known.
And people also say that UAN is equal to UNB.
Right?
AN is equal to NB.
Here.
AN is this angle is equal to this angle.
Next, let's do the calculation.
This angle is 150 degrees.
This angle is equal to 30 degrees.
The triangle AMN has two angles at the bottom.
Both are equal to 30 degrees.
Is this triangle heavy?
So AM is equal to AN.
This side is equal to this side.
Done?
So look at this.
Knowing this side, asking this side.
Did you learn how to calculate it?
I always look at the triangle MAN.
Look at it.
The triangle MAN is equal to the triangle ANB.
See?
ANB.
That's it.
In the case of the side, the side angle.
Can you see it?
Because this angle is equal to...
How many degrees, guys?
This angle is equal to 120 degrees.
That's it.
This angle is 90 degrees.
See?
ANB is also equal to 120 degrees.
It's equal in the case of two triangles.
Side, angle, side.
Right?
So you get the side MN is equal to the side AB.
Right?
And the result is equal to 100 volts.
UAB is equal to UMN is equal to 100 volts.
That's it.
This is the illusion when you use the connection method.
Do you see it?
Okay?
That's it.
See?
The following sentence.
You read the first line.
Give the circuit as shown in the figure.
Give the applied voltage of the two sides AB is equal to the applied voltage of the two sides NB is equal to 175 volts.
That is, U is the whole circuit and UC is equal to 175 volts.
UAM is equal to UMN is equal to 25 volts.
Find the phi code, that is, the code of the flux between UAB and Y.
This code is called the flux coefficient in the circuit.
You will know it later.
Look.
This code was given to you in the R-L-R-C multiplexed circuit.
That is, does the circuit have a transceiver of other circuits?
See?
This code was given to you.
And this code was solved for you in the numerical method.
Why do I do the numerical method in that code?
That is, this equation does not give any initial condition.
Right?
And when we do not give any initial condition,
we have to do it according to the numerical method.
That is the fastest and most perfect way.
Right?
But I still give this code in the method of vector multiplication.
Let me tell you that even if you are lazy to solve the numerical method,
you can still solve this code.
But you should not solve this code.
I just solve it for fun.
Right?
To feel the power of the multiplication.
But this code should be solved according to the numerical method.
Because the multiplication is only strong when the circuit has an initial condition.
If it does not have an initial condition,
the numerical method is still perfect.
Right?
Now, let's see how to solve this code.
You can solve this code only when the circuit is strong.
The starting point of the circuit is point A.
After that, from A to M, go through ER.
Right?
Next, from M to N, go through LR.
And I have already taught you, right?
LR, you draw it.
It is a diagonal line.
Right?
You do not have to explain much.
You do not have to explain that L is up and R is horizontal.
When L is up and R is horizontal,
our MN is still a diagonal line.
Right?
Then, from N to B, go down.
And now, is it too much or not?
It must be too much.
Because UNB is UC, 175.
Meanwhile, UMN is only 20 years.
UL is definitely smaller than UMN.
Right?
It is smaller than 2 years.
But UNB is 175.
So, definitely, our UC is very long.
Right?
Downward and very long.
Right?
Here.
This is the end of our circuit.
It is NB.
Is it done?
The result is AM by MN is equal to 20 years.
Right?
Here, I write the data.
This is 25.
This is also 25.
Is it done?
This is 175.
Right?
And our AB is also 175.
You connect them from A to B.
See?
Right?
Our AB is also 175.
So, it is a bit concave.
Now, look at this.
Do you see this triangle?
It is very difficult to solve.
And our phi angle is here.
Our phi angle is here.
I know that this triangle is difficult to solve.
Right?
So, of course, you can solve it.
How can you solve it?
Look at this.
2525.
175175.
Where will you put your hand?
The feeling of solving is very important.
It is the feeling of putting your hand.
Right?
And specifically, it is putting your hand.
What will you connect and what will you draw?
Sometimes, we only need to change one line.
It is very different.
Right?
One line is too different.
You will connect M and B.
Right?
This is the most important line in this circuit.
Right?
After you connect M and B, what do you have?
You have two triangles equal to each other.
Triangle AMB is equal to triangle NMB.
In the case of triangles,
triangles, triangles,
three triangles are equal to each other.
Right?
So, look at this.
So, these two triangles are equal to each other.
This is phi angle.
This angle is also phi.
Two triangles are equal to each other.
So, our two corresponding angles are also equal to each other.
Right?
Continue.
Of course, I can't calculate phi directly.
Because I don't know about MB.
If I know about MB, it will be easier.
It will be easier to apply the Hamkot theorem.
Right?
Next, you have to find where the arm is.
You have to find where the arm is.
You pull the triangle here.
Do you get it?
Pull the triangle AM to the triangle H.
So, how do you solve this?
Look at this.
Do you have this phi?
This phi is in the triangle AHB.
This phi is in the triangle NMH.
Right?
So, this is the way to solve this equation.
So, the angle MH is X.
You have to see this angle, this angle, this angle.
Then, put it in two triangles to solve it.
That's the way to solve it.
If you see two triangles are equal to each other,
it's still normal.
Right?
It's still normal.
There are many ways to prove that two triangles are equal to each other.
It's not necessary that two triangles are equal to each other.
There are many ways.
It's like calculus.
You connect ANB to it.
You can see that it's the triangle ANB.
Right?
It's a triangle.
So, our BM is...
What is it?
Our BM, as you can see,
it's the high line in this triangle.
And AM is the high line.
So, this is the axis.
Right?
Our M is the axis.
That's the good thing.
There are many properties that you can explore.
Alright.
OK.
So, look at this.
Do you have this phi?
Alright.
Look at this.
We have sin binh phi
plus cos binh phi
is equal to 1.
Got it?
What is sin binh phi used in this triangle?
This triangle.
Right?
Sin is opposite to the axis.
Right?
X binh is divided by 25 binh.
Right?
Cos binh phi.
Cos is the angle divided by the axis.
Right?
Right.
Cos is used in triangle AHB.
25 plus X.
All binh.
Divided by our axis
is 175 binh.
Equal to 1.
Right?
From here, you go to X
and you will get the phi.
The task is to find the phi.
Our X.
You press it.
It's a lot.
According to my memory,
when I was teaching this lesson,
it was R, L, C.
It's not pure.
It's 24.
Right?
Let's press it.
Alright.
24 binh plus 25 binh.
I remember this lesson very well.
Both lessons are good.
Right?
But of course, you have to know that
it's 24.
You have to know that
you shouldn't solve this problem
using the equation method.
Because it's not easy for you
to see the triangles
are the same
and these two are like this.
Right?
It's hard to solve the equation.
You need to think more than solving the equation.
You can solve the equation.
But you need to think more about the equation.
Right?
At the beginning.
X is 24.
From there, you get cos phi.
If you can solve the equation,
it will be shorter than solving the equation.
Solving the equation is a piece of cake.
Got it?
It's a piece of cake.
Right?
25 plus 24
divided by 175.
Got it?
It's 7 divided by 2.
Right?
You can watch the video
about R, L, C.
It's not pure.
I've written this equation
using the equation method.
Okay.
See?
The next question.
For the electric field as shown,
our field is C
connected to L, R
connected to electric field R.
Our current
is 1 ampere.
U M N is 90 degrees with U A B.
U A N is 30 degrees with U A B.
Find the electric field in R.
We know that
AB is equal to
AM is equal to
50.3 volts.
So,
you just need to find
U R.
Divide it by I
and you get
R.
So,
you can see
that this equation
has 2 angles.
Its sign
is
following the equation method.
Right?
Specifically,
we will make
a connected equation.
There are only 2 types of equations.
They are
neutral and connected.
We can't make
a neutral equation.
Right?
Actually, we can,
but it's a bit difficult.
It's not convenient
to make a neutral equation.
Okay?
Let's start.
This is point A.
From A to M,
we have U C.
Our U C
is going down.
Okay?
Here.
I've taught this lesson before.
I know that
I have to draw
this U C
quite long.
So,
the most difficult thing
that you need to do
is to learn by yourself.
Okay?
You may think
it's beautiful,
interesting,
and easy.
But,
it's difficult
to do it yourself.
Okay?
Then,
from M to N,
it goes through
L and R.
So, I draw R first.
Don't let it meet L.
Okay?
See?
There.
After U and L go up,
I still say
that the task is
to know
if it's too much or not.
So,
the equation method 90
will tell you
if it's too much
or not.
Okay?
Here.
I draw R.
And I know that
it's not too much.
Okay?
And you have to do it yourself.
Then,
from N to B,
it goes through U and R.
See?
Why do I know
it's not too much?
Because
M and N
will meet A and B.
Do you see this diagram?
In this diagram,
M and N and A and B
have a chance
to meet each other.
If you draw too much,
if you connect them,
they won't have a chance
to meet each other.
You have to try to draw too much.
You have to try it yourself.
Because
when you learn to draw,
you have to do it yourself.
Before I teach you,
you have to
do it yourself.
Okay?
Then,
connect from A to B.
Done?
And AB is equal to
50 times 3.
Done?
Next,
our AN
is here.
Convert 30 degrees
to AB.
Look at this.
Our AN
is connected,
right?
There.
Convert 30 degrees
to AB.
So,
this angle
is
the angle
of 30 degrees.
Next,
our MN
is the angle
of AB.
So,
you have to draw a little higher
so that the angle
will be more beautiful.
Okay?
Just accept it.
Okay?
Our MN,
you can just
imagine
that it can be square.
Square here.
Now,
it looks a bit fake.
But still,
accept that it is square.
Okay?
So,
you will look for
the small ur.
What is the small ur?
It is the edge of MH.
See?
It is the edge
of this square.
And this square
is the big ur.
Find this edge.
Find what?
The length of this triangle
is also very good.
Right?
You have two edges.
You have this angle.
Do you have this angle?
Four elements
in the equation.
And these two edges
are the same.
50.3
See?
So,
the triangle
M
A
B
is a triangle
at the top of A.
So,
these two edges are the same.
Right?
Continue.
This angle
is the most important feeling
in the equation.
Right?
Connect it.
This is also a square.
Set it as K.
Right?
So,
look at the equation
MN
is square with AB.
NB
is also square with AM.
So,
prove that
N
is the center
in the triangle
AMB.
Is it the center?
If it is the center,
then
AN
is the height.
Connect from the top
to the center
is it the height?
AN
is the height.
While
the height
originates from the top
of the triangle.
So,
the height
is also a square.
The two equations
are similar.
Again,
N is the center
because
MN
is square with AB
and NB
is square with AM.
N is the center.
So,
AN
is the height.
So,
the height
originates from the top
of the triangle.
Right?
So,
it is a square.
It is a square.
The height
originates from the top
of the triangle.
So,
it is a square.
So,
this square
is 30.
This one is also 30.
So,
this triangle
is a triangle.
Quite a lot of equations.
This triangle
is a triangle.
AMB
is a triangle.
Meanwhile,
there is a top
which is 60 degrees.
So,
this triangle is even.
Right?
It gives a lot of
overlapping equations.
And your task
is to find
MH
which is
30 degrees.
Right?
So,
this angle
is also
30 degrees.
Right?
So,
the angle
AK
is opposite
the angle
30 degrees
by half the angle
H.
So,
the angle
AK
is 25.3.
So,
the angle
AK
is
25.3.
Next,
triangle AKN
is a triangle.
It is a square.
Right?
So,
the angle
AKN
is
30 degrees.
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN
is
25.3.
Right?
So,
the angle
AKN