Question

2cos^2x+3cosx-2=0 ...?

Answer 1

Its like a polynomial.
 
cosx=x

so it'll be like

2x^2+3x-2=0

(2x−1)(x+2)

which makes your life easy because you do not have to solve cos(x)=−2 because it cannot be, so only solve cos(x)=1/2