Hi can anyone help me with this?
Thanks.
Prove the identity:
$\displaystyle cos3\theta = 4cos^3\theta - 3cos\theta$
[HINT: Express $\displaystyle cos3\theta$ as $\displaystyle cos (2\theta + \theta$]
hope,this link may help you
http://www.mathhelpforum.com/math-he...dentities.html
Ok i've got it down to:
$\displaystyle 2cos^3\theta - cos\theta - 2sin^2\theta cos\theta$
Im trying to use the identity of $\displaystyle sin^2\theta = 1 - cos^2\theta$
But im unsure how to use the identity as is is $\displaystyle 2sin^2\theta$
Thanks again