(cosα+sinα)*(cosα-sinα)*(1+tanαtan2α)三角函数

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(cosα+sinα)*(cosα-sinα)*(1+tanαtan2α)
三角函数

原式=[(cosα)^2-(sinα)^2]*(1+tanαtan2α)
=cos2α(1+tanαtan2α)
=cos2α+tanαsin2α
=cos2α+sinα/cosα*2sinαcosα
=cos2α+2(sinα)^2
=(cosα)^2-(sinα)^2+2(sinα)^2
=(cosα)^2+(sinα)^2
=1.

(cosα+sinα)*(cosα-sinα)*(1+tanαtan2α)
=(cos^2 α-sin^2 α)*(1+tanαtan2α)
=cos2α*(1+sinα/cosα sin2α/cos2α)
=cos2α+sinα/cosα*2sinαcosα
=cos2α+2sin^2α
=cos^2α-sin^2α+2sin^2α
=cos^2α+sin^2α
=1