Reflection of Math Video

ANGLE

 Angle is two rays connected in same point.

First ray is initial ray, and the second ray is terminal ray.

Vertex is a parts on an angle that connects two rays.

Direction the terminal side goes in

-positive angle, if an angle is generated by a-counter clockwise rotation.
-negative angle, if an angle is generated by a clockwise rotation.

To measure an angle, need to know how far terminal side rotates from the initial side.
To measure amount of rotation for an angle, we use x,y graph

 
x-axis is positive on right side of y-axis and negative on other side.
y-axis is positive above x-axis and negative below it.
Angle getting bigger if counterclockwise.

Angle can be measured by two unit, the units are:

1. Radian
2. Degree

There are some angles that called special angle, the angles is:

0˚, 30˚, 45˚, 60˚, 90˚. It is important to memorize special angle.