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Home > Education > Homework Help > Math & Sciences   »   how do i prove this identity

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Old Nov 5, 2009, 04:27 PM
sgmartin
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how do i prove this identity
sin2x/sinx - cos2x/cosx = secx

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Old Nov 5, 2009, 05:17 PM   #2  
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Remember these important identities:

sin2x = 2sinxcosx
cos2x = cos^2x - sin^x
= 2 cos^x - 1
= 1-2sin^2x.

That second identity for cos2x looks promising, since you will be dividing by cosx. Try it, and see if you make progress.
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