Trigonometric Functions Using Coordinate Systems:

Angle q is in standard position if its vertex is at the origin and its initial side is on the x-axis.

"q is in Q1 " means that angle q is in standard position and its terminal side is in quadrant 1.

If the terminal side is on an axis not in a quadrant, this angle is called a quadrantal angle or a between quadrant angle.

If q is in Q1 and it is an acute angle, then the previous trigonometric functions can be applied.

Let P = (x , y) be any point on the terminal side of q , and the distance r from the origin to point P is: