Question

Write Cos(3pi/2 - theta) in terms of cosine by using trig identities

Answer 1

hint:

cos(x-y) = cos(x)*cos(y) + sin(x)*sin(y)

Answer 2

another hint: using the unit circle, you will see that


cos(3pi/2) = 0

sin(3pi/2) = -1

Answer 3

but that gets you -sin theta which isn't in terms of cosine

Answer 4

well you could use the idea that cos(pi/2 - x) = sin(x), but that gets you back to the starting point in a way

Answer 5

also, sin^2(x) + cos^2(x) = 1

so you could solve for sin(x)