Trig Functions Problem?

Question

well its ask u to solve

cosY= -sqrt3/2

and

cosY= -sqrt3/2 for y in [pi,2pi]

can anyone explain how to do this i kinda forgot.

Answer 1

On the interval from y = pi to 2*pi,  cos(y) = -sqrt(3) / 2 at...

y = 7/6 pi

You might try taking a look at either a trig function value table or the unit circle.

Take care,

David

Answer 2

do you use the unit circle? if you do, go around the whole way and find all the areas that cosine is equal to -sqrt3/2, in this case it would be 5pi/6 and 7pi/6