i know that Cosh(x) = (E^x + E^-x ) / 2(adsbygoogle = window.adsbygoogle || []).push({});

how do i prove that Cosh(x) = Cos(ix) , where i is the imaginary unit

similarly Cosh(ix) = Cos(x)

and Sin(ix) = i Sinh(x)

similarly Sinh(ix) = i Sin(x)

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# How to prove that Cosh(x) = Cos(ix)

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