---
title: math.cosh
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/functions/math-trig/math-cosh
---

```
FLOAT math.cosh(FLOAT x)
```

**Available in:** all subroutines

Computes the hyperbolic cosine of its argument `x`.

## Parameters

`x` - Floating point value representing a hyperbolic angle.

## Return Value

Upon successful completion, this function returns the hyperbolic cosine of `x`.

If `x` is `math.NAN`, a NaN will be returned.

If `x` is ±0, the value 1.0 will be returned.

If `x` is `math.POS_INFINITY` or
`math.NEG_INFINITY`,
`math.POS_INFINITY` will be returned.

If the result would cause an overflow, a range error occurs and `math.cosh()`
will return the value
`math.POS_HUGE_VAL`.

## Errors

If the result would cause an overflow, then
`fastly.error` will be set to `ERANGE`.

## Example

```vcl
declare local var.fo FLOAT;

set var.fo = math.cosh(0);
```