Next: About this document ...

Trig Functions of Angles

a) Recall that the sine function is positive in Quadrants I and II, the cosine function is positive in Quadrants I and IV, and the tangent function is positive in Quadrants I and III.

b) In addition, the reference angle for is

1. , if .

2. , if .

3. , if .

4. , if .

c) If is an angle in standard position, and is a point on the terminal side of (other than the origin), then

and

where

Ex 1 Find .

Sol The reference angle for is . Since the sine is negative in Quadrant IV, .

Ex 2 Find .

Sol The reference angle for is . Since the cosine is negative in Quadrant III, .

Pr 1 Find .

Pr 2 Find .

Pr 3 Find .

Pr 4 Find .

Pr 5 Find .

Pr 6 Find .

Pr 7 Find .

Pr 8 Find .

Pr 9 If is an angle in standard position with the point on its terminal side, find and .

Pr 10 Find .

Pr 11 Find .

Next: About this document ...
Lawrence Marx 2002-07-14