sqrt

(PHP 4, PHP 5)

sqrtRacine carrée

Description

float sqrt ( float $arg )

Retourne la racine carrée de arg.

Liste de paramètres

arg

L'argument à traiter

Valeurs de retour

La racine carrée de arg ou la valeur spéciale NAN pour les nombres négatifs.

Exemples

Exemple #1 Exemple avec sqrt()

<?php
// La précision dépend de votre directive precision
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

Voir aussi

  • pow() - Expression exponentielle

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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
22 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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