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Cos(x) = cosh(x)?

by contempquant
Tags: cos, cosh
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contempquant
#1
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:

[tex]cos(x)=\frac{(e^{ix}+e^{-ix})}{2}[/tex]

and

[tex]cosh(x)=\frac{(e^{x}+e^{-x})}{2}[/tex]



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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Dick
#2
Mar12-11, 07:30 AM
Sci Advisor
HW Helper
Thanks
P: 25,228
It shows cosh(ix)=cos(x), not cosh(x)=cos(x). There's nothing wrong with that.


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