cos()
The cos()
CSS function is a trigonometric function that returns the cosine of a number, which is a value between -1
and 1
. The function contains a single calculation that must resolve to either a <number>
or an <angle>
by interpreting the result of the argument as radians. That is, cos(45deg)
, cos(0.125turn)
, and cos(3.14159 / 4)
all represent the same value, approximately 0.707
.
Syntax
css
/* Single <angle> values */
width: calc(100px * cos(45deg));
width: calc(100px * cos(0.125turn));
width: calc(100px * cos(0.785398163rad));
/* Single <number> values */
width: calc(100px * cos(63.673));
width: calc(100px * cos(2 * 0.125));
/* Other values */
width: calc(100px * cos(pi));
width: calc(100px * cos(e / 2));
Parameter
Return value
The cosine of an angle
will always return a number between −1
and 1
.
- If
angle
isinfinity
,-infinity
, orNaN
, the result isNaN
.
Formal syntax
Examples
Keep the size of a rotated box
The cos()
function can be used to keep the size of a rotated box.
When the element is rotated using rotate()
, it goes beyond its initial size. To fix this, we will use cos()
to update the element size.
For example, if you rotate a 100px
/100px
square 45deg
, the diamond it creates will be wider and taller than the original square. To shrink the diamond into the box allotted for the original square, you would have to scale down the diamond using this formula: width = height = 100px * cos(45deg) = 100px * 0.707 = 70.7px
. You need to also adjust the transform-origin
and add translate()
to correct the position:
HTML
html
<div class="original-square"></div>
<div class="rotated-diamond"></div>
<div class="rotated-scaled-diamond"></div>
CSS
css
div.original-square {
width: 100px;
height: 100px;
background-color: blue;
}
div.rotated-diamond {
width: 100px;
height: 100px;
background-color: red;
transform: rotate(45deg);
}
div.rotated-scaled-diamond {
width: calc(100px * cos(45deg));
height: calc(100px * cos(45deg));
margin: calc(100px / 4 * cos(45deg));
transform: rotate(45deg);
transform-origin: center;
background-color: green;
}
Result
Specifications
Specification |
---|
CSS Values and Units Module Level 4 # trig-funcs |
Browser compatibility
BCD tables only load in the browser