The Interesting Video of Math Content

At the beginning of April  we met again with Mr. Marsigit, he showed us again about five videos of math. There were very interesting videos. He has a lof of videos in his laptop. I think he always has some interesting methods to teach us.
There was some reflection of his videos.

First is English_angle.flv

Parts of an Angle

The corner point of an angle is called the vertex
And the two straight sides are called arms
      (at the top is initial side and at the bottom is terminal side)
      The angle is the amount of turn between each arm.

   

Measure of Angle

We can know the measure of angle by direction the terminal side goes in :

There is positive (+) direction.           
if an angle is generated by a-counter clockwise rotation.
The measure of the angle is 130⁰           
So there is positive angle

There is negative direction.
if an angle is generated by a clockwise rotation.
The measure of the angle is 360⁰-130⁰=230⁰
So there is negative angle
   



If we draw x-y graph, we have four quadrants and we can measure the angle too.

From the picture we can see that the angle is getting bigger.       
  Angle D>Angle C>Angle B>Angle A
So if an angle is generated by a-counter clockwise rotation,  the angle is getting bigger and bigger .

 

We can  measure angle by two ways, there are :
1.    Degree
2.    Radian

There is an example of the measure of special angle in degree and radian :

I hope we can memorize the special angle, because it`s very important ^_^

Second, English_Degrees.flv

A degree usually denoted by ° (the degree symbol), is a measurement of plane angle, representing 1⁄360 of a full rotation.
360° can make a circle, we call it full rotation.
The picture shows 90°, it is the same as 90/360.
90° is ¼ revolution.
We call it right angle.
If we sum, 90°+90°=180°
And we call it straight angle.

To measure angle we use radian and degree. It`s important to us to convert it.

Convert degree to radian

360°=2  radians
Simplify equation
180°=   radians
1°=  /180 radians

Convert radian to degree

2  radians=360°
Simplify equation
  radians=180°
1 radian =180°/

Okay, now we will apply it to solve some problems

120°= ... rad ( we can write radian just rad)
Remember : 1°=  /180 radians
120 x 1° = 120 ( /180 rad)
120°=2/3  rad

11/12   rad= ... °
Remember 1 radian =180°/
11/12   x 1 rad= 180°/  x 11/12 
11/12   rad= 165°

Third, Multiplying_exponent.flv

Rule #1 (Some both base and multiply base)

Example :
3^5 x 4^5     = (3x4)^5
    = (12)^5
    = 12x12x12x12x12
    =248832
Before learning the next rules, it will be important to us if we know that
Raise to second power is square, and raise to third power is cube.

Rule #2 (Divide instead multiply)

Example :
63:23    = (6:2)3
    = (3)3
    = 3x3x3
    = 27

Rule #3 (Base number base power)

Example :
(2^3)^2    = 2(3x2)
    = (2)6
    = 2x2x2x2x2x2
    = 64

Rule #4 (Differential exponent, same number base)
anam = a(n+m)
Example :
23x25    = 2(3+5)
    = 28
    = 2x2x2x2x2x2x2x2
    = 256

Rule #5
an:am= a(n-m)
Example :
45:43    = 4(5-3)
    = 42
    = 4x4
    =16
Two hot tips to remember it ^_^

       





Fourth, Teacher_multi_division_math.flv
This video tells us about some methods to multliply and division
Standard Algorithm for multification
26×31= …

We can solve this problem with different method
First,
26x 31 = (20x31) +(5x31) + (1x31)
20+5+1 = 26
10x31 = 310

20x31 = 620
5x31 = 155
1x31= 31
We sum it : 620 + 155 + 31 = 806

Second method is products method,

Third method is Lathice Method
26×31= …

26×31=806
Standard Algorithm for division
With long division we get 133 : 6 = 22 R.1 or 22 1/6
We can solve this problem with different method too
133 : 6 = ...
 First method,
6 x 10 = 60
6 x 20 = 120
6 x 1= 6
6 x 21 = 126
6 x 1 = 6
6 x 22 = 132
6 x 22 + 1 = 132 + 1
So 133 : 6 = 22 R.1

Second method,
6 x 10 = 60
6 x 10 = 60
6 x 1 = 6
6 x 1 = 6
6 x (10+10+1+1) = 6 (22) = 132
So 133 : 6 = 22 R.1

The last vidoe is about Quadratic Equation or quadratic_form.flv
(3x-1)(x+2) = 3x2+6x-x-2 = 3x2+5x-2 (it is basic quadratic form)
We can write : y=3x2+5x-2
The Standard quadratic form : y=ax2+bx+c
And Linear equation : y=mx+b
m is slope and b is y-intercept
Rate of change for quadratic equation is not constant

We can see that the slope changing over times
y=100-16x
at x=0 → y=100
at x=1→y=100-16=84
at x=2→ y=100-2.16=68
so, different point → different slope.