PHP 7.2.0 Alpha 2 Released


(PHP 4, PHP 5)

sqrtRadice quadrata


float sqrt ( float $arg )

Restituisce la radice quadrata di arg.

Example #1 Esempio di uso di sqrt()

// 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

jouhni at web dot de
12 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.

justin at hoogs dot com dot au
2 years 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.

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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