化简(sinθ-cosθ)/(tanθ-1)

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化简(sinθ-cosθ)/(tanθ-1)
化简(sinθ-cosθ)/(tanθ-1)

化简(sinθ-cosθ)/(tanθ-1)
(sinθ-cosθ)/(tanθ-1)
分子分母同乘以cosθ:
= cosθ(sinθ-cosθ)/(sinθ-cosθ)
= cosθ

负的COS瑟塔

=sinθ-cosθ)/(sinθ/cosθ-1)
=(sinθ-cosθ)/[(sinθ-cosθ)/cosθ]
=cosθ

原式=[-sinθ/(-tanθ)][1/(-cot θ)][cosθ/(-sinθ)]-sinθ =cos θsin θ/(cos θsinθ)-sinθ =sinθ-sinθ =0