sqrt

(PHP 4, PHP 5)

sqrtSquare root

Descrierea

float sqrt ( float $arg )

Returns the square root of arg.

Parametri

arg

The argument to process

Valorile întoarse

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

Exemple

Example #1 sqrt() example

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

A se vedea și

  • pow() - Exponential expression

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User Contributed Notes 2 notes

up
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
18 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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