Answers

2014-08-29T12:40:15+08:00
We use sin2x = 2sinxcosx and cos2x = 2cos^2 x - 1. We write: sin 2(2x) = 2sin2x(cos2x) = 2(2sinxcosx)(2cos^2 x - 1) = (4sinxcosx)(2cos^2 x - 1) = (8sinxcos^3 x) - (4sinxcosx).
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2014-08-30T05:08:24+08:00