##### Math trigonometric functions

- math.acos()
- math.acosh()
- math.asin()
- math.asinh()
- math.atan()
- math.atan2()
- math.atanh()
- math.cos()
- math.cosh()
- math.sin()
- math.sinh()
- math.sqrt()
- math.tan()
- math.tanh()

# math.asin()

Computes the principal value of the arc sine of the argument *x*.

### Parameters

*x* - Floating point value. The value of *x* should be in the range -1 to 1 inclusive.

### Return Value

Upon successful completion, this function returns the arc sine of *x*, in the
range -`math.PI_2`

to `math.PI_2`

radians inclusive.

If *x* is `math.NAN`

, a NaN will be returned.

If *x* is ±0, *x* will be returned.

If *x* is `math.POS_INFINITY`

or `math.NEG_INFINITY`

, a domain error occurs and a NaN will be returned.

If *x* is subnormal, a range error occurs and *x* will be returned.

For finite values of x not in the range -1 to 1 inclusive, a domain error occurs and a NaN will be returned.

### Errors

- If the
*x*argument is finite and is not in the range -1 to 1 inclusive, or is`math.POS_INFINITY`

or`math.NEG_INFINITY`

, then`fastly.error`

will be set to`EDOM`

. - If the
*x*argument is subnormal, then`fastly.error`

will be set to`ERANGE`

.

### Format

```
FLOAT
math.asin(FLOAT x)
```

### Examples

1
2
3

declare local var.fo FLOAT;
set var.fo = math.asin(1.0);