化简(1+cos2a)/(tana/2-1/tana/2)

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化简(1+cos2a)/(tana/2-1/tana/2)化简(1+cos2a)/(tana/2-1/tana/2)化简(1+cos2a)/(tana/2-1/tana/2)(1+cos2a)/(ta

化简(1+cos2a)/(tana/2-1/tana/2)
化简(1+cos2a)/(tana/2-1/tana/2)

化简(1+cos2a)/(tana/2-1/tana/2)
(1+cos2a)/(tana/2-1/tana/2)
=2cos^2 a/{[(tana/2)^2-1]/tana/2}
=cos^2 a/{[(tana/2)^2-1]/(2tana/2)}
=cos^2 a/[1/(-tana)]
=-cos^2a *tana
=-cosasina
==1/2sin2a

(1+cos2a)/(tana/2-1/tana/2)
=2cos²a/[(sin²a/2-cos²a/2)/(sina/2cosa/2)]
=2cos²a/(-2cosa/sina)
=-sinacosa
=-(1/2)sin2a