sqrt

(PHP 4, PHP 5)

sqrtQuadratwurzel

Beschreibung

float sqrt ( float $arg )

Berechnet die Quadratwurzel des Parameters arg.

Parameter-Liste

arg

Der zu verarbeitende Wert

Rückgabewerte

Die Quadratwurzel des Parameters arg oder der spezielle Wert NAN für negative Eingabewerte.

Beispiele

Beispiel #1 sqrt() Beispiel

<?php
// Die Anzahl der Nachkommastellen hängt von der 'precision' Einstellung ab
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

Siehe auch

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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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