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Cos(x) = cosh(x)?

by contempquant
Tags: cos, cosh
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Mar12-11, 07:15 AM
P: 13
1. The problem statement, all variables and given/known data

2. Relevant equations
from the identities found on the internet:




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
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Mar12-11, 07:30 AM
Sci Advisor
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P: 25,246
It shows cosh(ix)=cos(x), not cosh(x)=cos(x). There's nothing wrong with that.

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