# Unofficial LSL Reference

## [[functions:llasin]]

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## Function: llAsin

`float llAsin(float arg)`

Return the inverse sine of the argument, in radians. The inverse sine (also known as arcsine) is the angle whose sine is the given argument.

## Parameters

#### arg

Number whose inverse sine is to be found.

## Return value

Float number with the angle in radians that is the inverse sine of the argument.

• The range of `arg` must be between -1 and 1, because the sine of any angle can't be outside that range.
• The result is always between -PI_BY_TWO and [PI_BY_TWO, or NaN if the argument is out of the valid range.

## Short examples

```float angle;
angle = llAsin(1); // Sets angle to PI_BY_TWO, because the sine of 1 is PI_BY_TWO.
angle = llAsin(0); // Sets angle to 0, because the sine of 0 is 0.
angle = llAsin(-1); // Sets angle to -PI_BY_TWO, because the sine of -PI_BY_TWO is -1.
angle = llAsin(0.67); // Sets angle to approximately 0.734209 (the sine of that is 0.67)

angle = llAsin(2);  // Under Mono, sets angle to NaN (Not a Number)
// because there's no number whose sine is 2.
// Crashes with a math error under LSO.```

## Complete examples

The following example will output the pitch and roll angles of a prim, in degrees:

llAsin-example.lsl
```default
{
state_entry()
{
rotation rot = llGetLocalRot();
vector forward = <1,0,0>*rot;
vector right = <0,-1,0>*rot;

float pitch = llAsin(forward.z);
float roll = llAsin(right.z);

llOwnerSay("Pitch=" + (string)(pitch * RAD_TO_DEG) + "°; roll=" + (string)(roll * RAD_TO_DEG) + "°");
}
}```

## See also

• `llSin` calculates the sine of the argument.
• `llAcos` calculates the inverse cosine of the argument.
• `llCos` calculates the cosine of the argument.
• `llAtan2` calculates the angle of a 2D vector.
• `llTan` calculates the tangent of the argument.
• Other `math` functions 