已知sinθ+sin∧2(θ)=1,求3cos∧2(θ)+cos∧4(θ)-2sinθ

题目

已知sinθ+sin∧2(θ)=1,求3cos∧2(θ)+cos∧4(θ)-2sinθ

答案

sinθ+sin^2θ=1
sinθ=1-sin^2θ=cos^2θ
3cos^2θ+cos^4θ-2sinθ
=3sinθ+sin^2θ-2sinθ
=sin^2θ+sinθ
=1