Standard position of an angle  trigonometry
In trigonometry an angle is usually drawn in what is called the "standard position" as shown below.
In this position, the
vertex of the angle (B) is on the
origin
of the x and y
axis. One side of the angle
is always fixed along the positive xaxis  that is, going to the right along the axis in the 3 o'clock direction (line BC).
This is called the
initial side of the angle.
The other side of the angle is called the
terminal side.
See also Angle definition and properties  Trigonometry
Other trigonometry topics
Angles
Trigonometric functions
Solving trigonometry problems
Calculus
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