Question

sin^4a-cos^4a=1-2sin^2a

Answer 1

sin2θ=1−cos2θ and cos2θ=1−sin2θ as follows:

sin4θ+cos4θ=sin2θ(1−cos2θ)+cos2θ(1−sin2θ)=1−2sin2θcos2θ

Answer 2

Answer:

Step-by-step explanation:

=(Sin^2a)^2 -(sin^2a)^2

=(sin^2a+cos^2a)(sin^2a -cos^2a)

=sin^2a-cos^2a

=sin^2a-(1-sin^2a)

=2sin^2a-1