Question

sin⁴theta - cos⁴ theta= 1 -2 cos²theta




prove this

Answer 1

LHS = sin^4 θ−cos^4 θ

=(1−cos^2 θ)^2−cos^4 θ

=(1+cos^4 θ−2cos^2 θ)− cos^4 θ=

1−2cos^2 θ= RHS