Question

cos^2(x)-cos(x)=2

Answer 1

Let cos(x)=a, substitute "a" instead of cos(x)

cos^2(x)-cos(x)=2 becomes a^2-a=2.

Can you solve this quadratic or still need help>?

Answer 2

i am trying to solve it in the domain of 0 less than or equal to theta which is less than or equal to 2 pi.
what does x equal?

Answer 3

go on the way "SolomonZelman" says
you will find cos x=-1 ,-2
cos x=-2 has no solution
cos x=-1 so x=pi +2kpi
in [0,2pi]
x=pi only