atan()

The atan() CSS function is a trigonometric function that returns the inverse tangent of a number between -∞ and +∞. 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(atan(1));
transform: rotate(atan(4 * 50));

/* Other values */
transform: rotate(atan(pi / 2));
transform: rotate(atan(e * 3));

Parameter

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

number: A calculation which resolves to a <number>() between -∞ and +∞.

Return value

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

If number is 0⁻, the result is 0⁻.
If number is +∞ the result is 90deg.
If number is -∞ the result is -90deg.

That is:

atan(-infinity) representing -90deg.
atan(-1) representing -45deg
atan(0) representing 0deg
atan(1) representing 45deg
atan(infinity) representing 90deg.

Examples

Rotate elements

The atan() 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(atan(-99999));
}
div.box-2 {
  transform: rotate(atan(-1));
}
div.box-3 {
  transform: rotate(atan(0));
}
div.box-4 {
  transform: rotate(atan(1));
}
div.box-5 {
  transform: rotate(atan(99999));
}

css types atan()