（sin（180°+2x））/（1+cos2x）*（cos2x0/（cos（90°+2x））
＝[-sin2x/(1+cos2x)][cos2x/(-sinx)]
=(sin2xcos2x)/(sinx(1+cos2x))
=(sin2xcos2x)/[2snxcos²x]
=(sin2xcos2x)/sin2xcosx
=cos2x/cosx
（sin（180°+2x））/（1+cos2x）*（cos2x0/（cos（90°+x））=
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