find x: 3cos 2x - 4cos2 x +2= 0

Question

find x: 3cos 2x - 4cos² x +2= 0

Answer 1

3cos 2x - 4cos^2 x +2= 0

 

There is a formula for cos2x=2cos^2x-1 (=1-2sin^2x)

 

Substituting for cos2x:

 

3(2cos^2x-1))-4cos^2x+2=0

 

2cos^2x-1=0

 

solve as in part b) of your previous question