Use identities to write the equation in terms of the single

Use identities to write the equation in terms of the single angle theta. Then solve equation for 0 lessthanorequalto 0

Solution

2(2cos^2x-1) =-4cos^2x

4cos^2x-4 = -4cos^2x

8cos^2x-4=0

4(2cos^2x-1) =0

2cos^2x -1 =0

cos^2x = 1/2

cosx= -1/ sqrt2 and 1/sqrt2

so x will be pi/4, 3pi/4, 7pi/4,5pi/4   answer