sqrt

(PHP 4, PHP 5)

sqrt평방 제곱근

설명

float sqrt ( float $arg )

arg의 평방제곱근을 반환합니다.

인수

arg

계산할 인수

반환값

arg의 평방제곱근이나, 음수일 경우엔 특수 값 NAN.

예제

Example #1 sqrt() 예제

<?php
// 정밀도는 precision 설정에 의존합니다.
echo sqrt(9); // 3
echo sqrt(10); // 3.16227766 ...
?>

참고

  • pow() - 거듭제곱 표현

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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
21 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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