How can I prove 4(sin^4 x+ cos^4 x) always equals cos 4x + 3? I don't think I've been taught the identities that I need... Thanks in advance
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Originally Posted by ctt How can I prove 4(sin^4 x+ cos^4 x) always equals cos 4x + 3? I don't think I've been taught the identities that I need... Thanks in advance Yeah, maybe not, its ugly but this one is most directly solved with $\displaystyle \cos(x)=\frac{e^{ix}+e^{-ix}}{2}$ and $\displaystyle \sin(x)=\frac{e^{ix}-e^{-ix}}{2i}$
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