Question

If cos θ = 4/5, find cos (-θ)

a. 4/5

b. 1/5

c. 5

d. -1/5

e. -4/5

How do i figure this out? Is it simply -4/5? or do i need to refer to the unit circle?

Answer 1

well recall from your unit circle that cosine relates to the x-coordinate of your point.

Answer 2

So if we spin the opposite direction (that's what the negative tells us to do), then what happens to our x-coordinate?