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# Description

Returns the arc sine (aka inverse sine) of an input

Arc sine is the inverse function for sine. That is, given a value for va= l in the domain [-1.0, 1.0], it will return an angle asin(val) in degrees.<= /p>

To illustrate, picture the unit circle (a circle of radius 1.0 centered = about the origin). If you imagine a unit vector rotating inside of the unit= circle, the y-coordinate of the endpoint of the vector is the asin functio= n argument val. The angle that the vector makes with the positive x-axis is= the function output asin(val). As the vector rotates inside the circle, th= e y-coordinate of the vector must always be within the unit circle, so the = input argument to asin (aka val) must be within [-1.0, 1.0] to be meaningfu= l.

Also, as sin(t) is doubly valued for t in [-180, 180], the asin function= is restricted to quadrant IV and quadrant I. This means that the unit vect= or rotating inside the unit circle is assumed to have a positive or 0 x-coo= rdinate, therefore asin(val) always returns a value in [-90, 90].

Math

# Command syntax

## Syntax

=20 =20
 asin value

### Arguments

=20 =20 =20 =20 =20 =20
`value` float yes The domain of arc sine is [-1.0, 1.0]. Values of= val outside of this domain are not meaningful to the function asin.

None

## Return value

float

For an input argument val in [-1.0, 1.0], returns a floating point angle= (degrees) in the range [-90.0, 90.0]. For input arguments t in the ranges:= (1.0, Inf], [-Inf, -1.0) and NaN, asin(t) returns NaN.

## Examples

```float \$t;float \$asin_of_t; float \$sin_of_asin_of_t;// asin=
(1.0) is 90 degrees because sin(90 degrees) =3D 1.0\$t                =
=3D 1.0;\$asin_of_t        =3D asin(\$t);\$sin_of_asin_of_t =3D sin(\$a=
sin_of_t);print("t, asin(t), sin(asin(t)) =3D " + string(\$t) + ", " + s=
tring(\$asin_of_t) + ", " + string(\$sin_of_asin_of_t));// 1.1 is not a m=
eaningful input into asin and will return // NaN (-1.#IND00)\$t =3D -1.1=
;\$asin_of_t        =3D asin(\$t);\$sin_of_asin_of_t =3D sin(\$asin_of_=
t);print("t, asin(t), sin(asin(t)) =3D " + string(\$t) + ", " + string(\$=
asin_of_t) + ", " + string(\$sin_of_asin_of_t));```