1+cos2x-cos^2x =cos^2x

Question

i know that cos(a-b) = cosacosb+sinasinb And cos(a+b) = cosacosb-sinasinb

 

and cos(x+x) = cos^2x-sin^2x

Answer 1

Try rearranging so that cos(2x) is by itself on one side of the equation,

 

and using the identity cos(2x) = 2cos^2(x) - 1

 

That leads directly to the solution.