Question

Suppose cos(a)=4/5. use the trig identity sin^2(a)+cos^2(a)=1 to find sin(a) in quadrant IV.

Answer 1

sin a = -3/5

Explanation:

sin^2(a)+cos^2(a)=1

sin^2(a)+ (4/5)^2 = 1

sin^2(a) = 1 - 16/25 = 9/25

sin a = 3/5 ( in Quadrant 1)

In quadrat IV the sine is negative

so sin a = -3/5