sqrt

(PHP 4, PHP 5)

sqrtSquare root

Description

float sqrt ( float $arg )

Returns the square root of arg.

Parameters

arg

The argument to process

Return Values

The square root of arg or the special value NAN for negative numbers.

Examples

Example #1 sqrt() example

<?php
// Precision depends on your precision directive
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

See Also

  • pow() - Exponential expression

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User Contributed Notes 2 notes

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7
jouhni at web dot de
10 years ago
To get any root of a number your can use the pow() function:

pow(8, 1/3)

which gives you the third root of eight.

Jouhni
up
1
justin at hoogs dot com dot au
20 days ago
As we all know, the square of the hypotenuse is equal to the sum of the squares of the other two sides of a right triangle (a2 + b2 = c2).

With that in mind I created a quick way to reduce images to a maximum area without messing up width/height constraints.

<?php
list($width_orig, $height_orig) = getimagesize($img);

$max_a = 500000; // maximum area in pixels

$width = $width_orig;
$height = $height_orig;

$area = $width * $height;
if (
$area > $max_a) {
   
$mult = sqrt($max_a) / sqrt($height * $width);
   
$width *= $mult;
   
$height *= $mult;
}
?>
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