`asin()` CSS function

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2023.

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 an <angle> between -90deg and 90deg.

Syntax

css

/* 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 a 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

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

body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 50px;
}

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));
}