Trig identity?

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November 10th 2012, 02:09 PM
WhatthePatel

Trig identity? (new one)

I need help with this one...
sin³A+cos³A/sinA + CosA = 1-sinAcosA
Thanks
November 10th 2012, 02:24 PM
Plato

Re: Trig identity?

Quote:

Originally Posted by WhatthePatel

I need help with this one...
sin³A+cos³A/sinA + CosA = 1-sinAcosA

Hint:
$x^3+y^3=(x+y)(x^2-xy+y^2)$
November 10th 2012, 03:19 PM
WhatthePatel

Re: Trig identity?

New identity?
sin3x = 3cos²xsinx-sin³x
November 10th 2012, 03:26 PM
skeeter

Re: Trig identity?

$\sin(3x) = \sin(2x+x) = \sin(2x)\cos(x) + \cos(2x)\sin(x)$

finish it using appropriate double angle identities.

... and, start a new thread for a new problem.

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