Question

cos2x =2 cos square -1​

Answer 1

$\huge\boxed{\fcolorbox{white}{pink}{Answer}}$

as we know that ..

$\Large\boxed{cos2x=cos^2x-sin^2x}$

==>. cos2x = cos^2x - ( 1 - cos^2x)

$\Large\boxed{sin^2x=1-cos^2x}$

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

==>. $\Large\boxed{cos2x=2cos^2x-1}$

I hope this will helps u bro...☺️