英CZ
在网上帮你找到了一个效,果很 好的痔疮治 疗产品
http://e.iciba.com/link.php?url=//abd.ryh.dr.ag/hsg?eejcazvjruravbffkvlcogjqzskski.
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以下髓不_葙.关
http://baike.baidu.com/view/159378.htm
三倍角公式推导
sin(3a)
=sin(a 2a)
=sin2acosa cos2asina
=2sina(1-sin^2a) (1-2sin^2a)sina
=3sina-4sin^3a
cos3a
=cos(2a a)
=cos2acosa-sin2asina
=(2cos^2a-1)cosa-2(1-cos^2a)cosa
=4cos^3a-3cosa
sin3a=3sina-4sin^3a
=4sina(3/4-sin^2a)
=4sina[(√3/2)-sina][(√3/2) sina]
=4sina(sin60° sina)(sin60°-sina)
=4sina*2sin[(60 a)/2]cos[(60°-a)/2]*2sin[(60°-a)/2]cos[(60° a)/2]
=4sinasin(60° a)sin(60°-a)
cos3a=4cos^3a-3cosa
=4cosa(cos^2a-3/4)
=4cosa[cos^2a-(√3/2)^2]
=4cosa(cosa-cos30°)(cosa cos30°)
=4cosa*2cos[(a 30°)/2]cos[(a-30°)/2]*{-2sin[(a 30°)/2]sin[(a-30°)/2]}
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