Question

Can someone explain the steps of this?

Answer 1

From the 2nd to 3rd line

Answer 2

are u there?

Answer 3

its called double angle identity, cos(2x)=cos^2(x)-sin^2(x)=(1-sin^2(x))-sin^2(x)=1-2sin^2(x)

Answer 4

sin(2x)=2cos(x)sin(x) is another one

Answer 5

Oh okay thank you :)