Question

sin4θ+cos4θ怎样化简?

Answer 1

本答案利用(sinθ)^2+(cosθ)^2=1解的，再配方

容易理解！容易明白！

(sinθ)^4+(cosθ)^4

=[(sinθ)^2]^2+[(cosθ)^2]^2+2[(sinθ)^2]*[(cosθ)^2]-2[(sinθ)^2]*[(cosθ)^2]

=[(sinθ)^2+(cosθ)^2]^2-2[(sinθ)^2]*[(cosθ)^2]

=...