sqrt

(PHP 4, PHP 5)

sqrtRaiz quadrada

Descrição

float sqrt ( float $arg )

Retorna a raiz quadrada de arg.

Parâmetros

arg

O argumento para processar

Valor Retornado

A raiz quadrada de arg ou o valor especial NAN para números negativos.

Exemplos

Exemplo #1 Exemplo da sqrt()

<?php
// Precisão depende de sua diretiva precision
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

Veja Também

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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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