### cosh =====================================================================

Tags
----
scripting, JS, internal, treenode, general concept

Parameters
----------
x

General description
-------------------
Returns the hyperbolic cosine of x

```
            exp(x) + exp(-x)
  cosh(x) = ----------------
                   2
```

###

Eval_cosh = ->
  push(cadr(p1))
  Eval()
  ycosh()

ycosh = ->
  save()
  yycosh()
  restore()

yycosh = ->
  d = 0.0
  p1 = pop()
  if (car(p1) == symbol(ARCCOSH))
    push(cadr(p1))
    return
  if (isdouble(p1))
    d = Math.cosh(p1.d)
    if (Math.abs(d) < 1e-10)
      d = 0.0
    push_double(d)
    return
  if (isZeroAtomOrTensor(p1))
    push(one)
    return
  push_symbol(COSH)
  push(p1)
  list(2)