Question

prove that cos4x=1-8 sin^2.cos^2x

Answer 1

Hey!!!....Here is ur answer

cos4x=cos2 (2x)

=1-2sin^2 2x

=1-2 (2sinx cosx)^2

=1-2 (4sin^x cos^2x)

=1-8 sin^2x.cos^2x

Hope it will help you