SOLUTION: Use Demoivre's theorem to prove that tan4x=((4tanx-3tan^(2)x))/(1-6tan^(2)x+tan^(4)x)

Question 1169171: Use Demoivre's theorem to prove that tan4x=((4tanx-3tan^(2)x))/(1-6tan^(2)x+tan^(4)x)
Answer by AnlytcPhil(1807) (Show Source): You can put this solution on YOUR website!

Is this what you mean?



If so, then this is not an identity.  For let x = 45°











That's false, so the equation is not an identity so we can't prove
what's false is true!

Edwin

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