atan()

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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.

Formal syntax

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

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

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

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

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

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

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));
}

Result

Specifications

Specification
Unknown specification
# trig-funcs

Browser compatibility

BCD tables only load in the browser

See also