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April 19, 2014

April 19, 2014

Posted by **Carl** on Monday, March 26, 2012 at 1:09am.

sin(x–y)sin(x+y)=sin^2(x)–sin^2(y)

- trig -
**Steve**, Monday, March 26, 2012 at 11:00am(sinx cosy - cosx siny)(sinx cosy + cosx siny)

= sin^2x cos^2y - cos^2x sin^2y

= sin^2x(1-sin^2y) - (1-sin^2x)sin^2y

= sin^2x - sin^2x sin^2y - sin^2y + sin^2x sin^2y

= sin^2x - sin^2y

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