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Trigonometry 16 Online
OpenStudy (anonymous):

I can't seem to figure this example out.....It's all worked out I just don't see how the identity works to reduce both of these in this way??? cos 3(theta) = cos^3(theta)-3cos(theta)sin^2(theta) and sin 3(theta) = 3 cos^2(theta)sin(theta)-sin^3(theta) USING cos^2(theta)+sin^2(theta)=1 identity then these both go to>> cos 3(theta)=4cos^3(theta)-3cos(theta) and sin3(theta)=3sin(theta)-4sin^3(theta)

OpenStudy (anonymous):

Here's the equation:

hartnn (hartnn):

\(\Large \cos^3(\theta)-3\cos(\theta)\sin^2(\theta)\) \(\Large \cos^2(\theta)+\sin^2(\theta)=1\implies \sin^2(\theta)=1-\cos^2(\theta)\) so, \(\Large \cos^3(\theta)-3\cos(\theta)[1-\cos^2(\theta)] \) do you get this ?

OpenStudy (anonymous):

Ok - yes, I see that.

OpenStudy (anonymous):

Thank you @hartnn :)

hartnn (hartnn):

welcome ^_^

hartnn (hartnn):

ask if anymore doubts ?

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