# Math Help - Hyperbolic Functions

1. ## Hyperbolic Functions

Hi
I'm new to hyperbolic functions so I'm a bit stuck on two problems which may seem easy. I don't know where to start. Any help would be greatly appreciated.

Show from the definitions of $\sinh(x)$ and $\cosh(x)$ that:

a) $cosh(2x) = 2\cosh^2(x) - 1$

and

b) $\sinh(x + y) = \sinh(x)\cosh(y) + \cosh(x)\sinh(y)$

P.S sorry if this is in the wrong area but I couldn't see any that were obviously for it.

2. $sh(x) = \frac{e^{x} - e^{-x}}{2}$

$sinh(x)$ or $sh(x)$

$ch(x) = \frac{e^{x} + e^{-x}}{2}$

$cosh(x)$ or $ch(x)$

now use this... and its easy