atan()

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)); 

Parameters

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 a 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-keyword> |
 ( <calc-sum> ) 

<calc-keyword> = 
 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

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)); } 

Result

Specifications

Browser compatibility

See also

• sin()
• cos()
• tan()
• asin()
• acos()
• atan2()