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January 29, 2015

January 29, 2015

Posted by **adil** on Tuesday, December 1, 2009 at 6:00pm.

(2cosx+1)(2cosx-1)= 1 +2cos2x

- trig -
**MathMate**, Tuesday, December 1, 2009 at 6:39pmUsing

cos(2x)=cos²(x)-sin²(x)

and cos²(x)=1-sin²(x)

expand the right-hand-side to

4cos²(x)-1

which easily factorizes to the left-hand-side, namely:

(2cosx+1)(2cosx-1)

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