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Section: Mathematical Functions
Computes the hyperbolic cosine of the argument. The syntax for its use is
y = cosh(x)
The cosh function is computed from the formula 
![\[ \cosh(x) = \frac{e^x+e^{-x}}{2} \]](form_62.png) 
 For x complex, it follows that 
![\[ \cosh(a+i*b) = \frac{e^a(\cos(b)+i*\sin(b)) + e^{-a}(\cos(-b)+i*\sin(-b))}{2} \]](form_63.png) 
Here is a simple plot of the hyperbolic cosine function
--> x = linspace(-5,5);
--> plot(x,cosh(x)); grid('on');
