2 quick sin/cos problems, solving for an angle

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December 15th 2008, 01:56 PM
gobbajeezalus

2 quick sin/cos problems, solving for an angle

http://img.skitch.com/20081215-j1yrj...1an72k92bu.jpg

Thanks!
December 16th 2008, 02:44 AM
mathaddict

Re :

(1) $sinx=cos2x-1$
$sinx=1-2sin^2x-1$
$sinx=-2sin^2x$
$sinx(2sinx+1)=0$
solve for $sinx=0$ and $2sinx+1=0$

(2) $sinx+cosx=0$ ]
$sinx=-cosx$
$tanx=-1$

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