sqrt

(PHP 4, PHP 5)

sqrtRadice quadrata

Descrizione

float sqrt ( float $arg )

Restituisce la radice quadrata di arg.

Example #1 Esempio di uso di sqrt()

<?php
// La precisione dipende dalle impostazioni delle direttive sulla precisione
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

Vedere anche pow().

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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
19 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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