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January 30, 2015

January 30, 2015

Posted by **mailon** on Thursday, September 4, 2008 at 10:29pm.

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

- trig -
**drwls**, Friday, September 5, 2008 at 5:11amLet x^2 = y

What you have written is equivalent to

1 - 2 sin y = cos y

which is not a correct identity.

It looks like you have put parentheses in the wrong places. The outside ones are unecessary.

A correct version would be

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

That is one of the double-angle identities

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