已知(2sin^2α+sin2α)/(1+tanα)=k,(π/4
问题描述：
已知(2sin^2α+sin2α)/(1+tanα)=k,(π/4
答
k=(2sin^2α+2sinαcosα)/(1+sinα/cosα)
=2sinα(sinα+cosα)/[(sinα+cosα)/cosα]
=2sinαcosα
(sinα-cosα)^2
=sin^2α-2sinαcosα+cos^2α
=1-k
π/4