Question

If 0 < f ≤ 90 and cos(22f − 1) = sin(7f + 4), what is the value of f?

A. f = 3
B. f = 4
C. f = 5
D. f = 6

Answer 1

cos(theta) = sin(90-theta)

so cos(22f-1) = sin( 90 - [22f - 1]) = sin(7f + 4)

since you now have sin on both sides you can set up

90 - (22f-1) = 7f + 4 and solve from there

Answer 2

ah ok, I got f = 3 as my final answer. thank you!