Ответы и объяснения

2014-02-17T19:10:24+00:00
1)   1-tgα*cosα*sinα=1-sinα÷cosα*cosα*sinα=1-sin²α=cos²α+sin²α-sin²α=cos²α
2)   2sinα*cosα=sin2α,⇒ cos2α÷sin2α=ctg2α
3)  2cos²α-1=cos2α
2014-02-17T19:10:33+00:00
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