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css function

`acos()` CSS function

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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 an angle between 0deg and 180deg.

Syntax

/* 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.

  • number
    • : A calculation which resolves to a &lt;number&gt; between -1 and 1.

Return value

The inverse cosine of a number will always return an angle between 0deg and 180deg.

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

Formal syntax

Examples

Rotate elements

The acos() 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

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

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

Interactive exampleOpen the canonical MDN source to run this embedded demo.

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also