The asin() CSS function is a trigonometric function that returns the inverse sine of a number between -1 and 1. The function contains a single calculation that returns the number of radians representing an <angle> between -90deg and 90deg.

Syntax

/* Single <number> values */
transform: rotate(asin(-0.2));
transform: rotate(asin(2 * 0.125));

/* Other values */
transform: rotate(asin(pi / 5));
transform: rotate(asin(e / 3));

Parameters

The asin(number) function accepts only one value as its parameter.

number

A calculation which resolves to a <number> between -1 and 1.

Return value

The inverse sine of an number will always return an <angle> between -90deg and 90deg.

• If number is less than -1 or greater than 1, the result is NaN.
• If number is 0⁻, the result is 0⁻.

Formal syntax

<asin()> = 
  asin( <calc-sum> )  

<calc-sum> = 
  <calc-product> [ [ '+' | '-' ] <calc-product> ]*  

<calc-product> = 
  <calc-value> [ [ '*' | / ] <calc-value> ]*  

<calc-value> = 
  <number>        |
  <dimension>     |
  <percentage>    |
  <calc-keyword>  |
  ( <calc-sum> )  

<calc-keyword> = 
  e          |
  pi         |
  infinity   |
  -infinity  |
  NaN        

Examples

Rotate elements

The asin() function can be used to rotate elements as it return an <angle>.

HTML

<div class="box box-1"></div>
<div class="box box-2"></div>
<div class="box box-3"></div>
<div class="box box-4"></div>
<div class="box box-5"></div>

CSS

div.box {
  width: 100px;
  height: 100px;
  background: linear-gradient(orange, red);
}
div.box-1 {
  transform: rotate(asin(1));
}
div.box-2 {
  transform: rotate(asin(0.5));
}
div.box-3 {
  transform: rotate(asin(0));
}
div.box-4 {
  transform: rotate(asin(-0.5));
}
div.box-5 {
  transform: rotate(asin(-1));
}

Result

Specifications

Browser compatibility

See also

• sin()
• cos()
• tan()
• acos()
• atan()
• atan2()