# Express Cos3x In Terms of Sinx

2
i was able to have it expressed in sine but there's a cosx that will be left on it.. cosx(1-4(sinx)^2).. are you to have it all in sine?
i am not sure of my answer .-.
i'm waiting my dear.. are you asked to express everything in sine?
if it says in terms of sine then there can be numerical values and only sin
so at least no cos

2014-11-21T22:17:08+08:00

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Cos(3x)=cos(2x+x)
cos(3x)=cos2xcosx-sin2xsinx
cos(3x)=1-sin²xcosx-2sinxcosxsinx
cos(3x)=1-2sin²x-2sinxsinx
I Think You Got It ..
the 4th line is what I am not so sure about...
Thanks StiLL :)
cos(3x) = (1-sin²x)cosx-2sinxcosxsinx.. remember that (1-sin²x) is a binomial.. cosx should be factored out. also it should be (1-2sin²x)..
but since it is cosx, how do we change it to sin..... if it says terms of sin, there hsould be no cos
2014-11-21T22:34:43+08:00
Check on the attached file