Question

Verify the identities.

cos(4u) = cos^2(2u) - sin^2(2u)
[cot^2(x)/csc(x)+1] = {1-sin(x)/sin(x)]
sin(x+ pi/2)=cos(x)
Plz help.

Answer 1

`cos(4u)=cos(2u+2u) \\ =cos(2u)cos(2u) - sin(2u)sin(2u) \\ = cos^(2) (2u)- sin^(2) (2u)`