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 .
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