acos()
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 acos() CSS function is a trigonometric function that returns the inverse cosine of a number between -1 and 1. The function contains a single calculation that returns the number of radians representing an <angle> between 0deg and 180deg.
Syntax
css
/* Single <number> values */ transform: rotate(acos(-0.2)); transform: rotate(acos(2 * 0.125)); /* Other values */ transform: rotate(acos(pi / 5)); transform: rotate(acos(e / 3)); Parameters
The acos(number) function accepts only one value as its parameter.
Return value
The inverse cosine of a number will always return an <angle> between 0deg and 180deg.
- If
numberis less than-1or greater than1, the result isNaN. - If
numberis exactly1, the result is0.
Formal syntax
<acos()> =
acos( <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 acos() 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
css
div.box { width: 100px; height: 100px; background: linear-gradient(orange, red); } div.box-1 { transform: rotate(acos(1)); } div.box-2 { transform: rotate(acos(0.5)); } div.box-3 { transform: rotate(acos(0)); } div.box-4 { transform: rotate(acos(-0.5)); } div.box-5 { transform: rotate(acos(-1)); } Result
Specifications
| Specification |
|---|
| CSS Values and Units Module Level 4 # trig-funcs |