Can someone prove this for me, please show enough steps so that i know what your doing along the way. Thanks

sin3x=3sinx-4sin^3x - the x isn't with ^3.

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- Jul 20th 2007, 11:36 PMfam600Help Proving double-angle identities
Can someone prove this for me, please show enough steps so that i know what your doing along the way. Thanks

*sin3x=3sinx-4sin^3x - the x isn't with ^3.*

- Jul 21st 2007, 12:20 AMred_dog
$\displaystyle \sin 3x=\sin (2x+x)$ and use the formula

$\displaystyle \sin(a+b)=\sin a\cos b+\sin b\cos a$

and $\displaystyle \sin 2x=2\sin x\cos x, \ \cos 2x=1-2\sin^2x$