# cos(x) = cosh(x)?

by contempquant
Tags: cos, cosh
 P: 13 1. The problem statement, all variables and given/known data 2. Relevant equations from the identities found on the internet: $$cos(x)=\frac{(e^{ix}+e^{-ix})}{2}$$ and $$cosh(x)=\frac{(e^{x}+e^{-x})}{2}$$ 3. The attempt at a solution Assuming for the definition of cosh(x), if we take x as being equal to (ix), then surely this shows that cosh(x)=cos(x)? Can someone explain why this is wrong please? because i can't see it
 Sci Advisor HW Helper Thanks P: 25,160 It shows cosh(ix)=cos(x), not cosh(x)=cos(x). There's nothing wrong with that.

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