(1/49)^cos2x=7^2-2cosx

Question

(1/49)^cos2x=7^2-2cosx

Answer 1

7^-2cos2x=7^2-2cosx
-2cos2x=2-2cosx
-4cos²x+2-2+2cosx=0
-4cos²x+2cosx=0
-2cosx(2cosx-1)=0
cosx=0⇒x=π/2+πn,n∈z
2cosx-1=0⇒cosx=1/2⇒x=+-π/3+2πk,k∈z