化简 cos 2a/tan(a+派/4)

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化简cos2a/tan(a+派/4)化简cos2a/tan(a+派/4)化简cos2a/tan(a+派/4)=cos2acos(a+π/4)/sin(a+π/4)=cos2a(cosa-sina)/(

化简 cos 2a/tan(a+派/4)
化简 cos 2a/tan(a+派/4)

化简 cos 2a/tan(a+派/4)
=cos2acos(a+π/4)/sin(a+π/4)
=cos2a(cosa-sina)/(cosa+sina)
=(cosa^2-sina^2)(cosa-sina)/(cosa+sina)
=(cosa-sina)^2
=1-sin2a