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# sqrt

(PHP 4, PHP 5)

sqrtSquare root

### Description

float sqrt ( float \$arg )

Returns the square root of arg.

### Parameters

arg

The argument to process

### Return Values

The square root of arg or the special value NAN for negative numbers.

### Examples

Example #1 sqrt() example

`<?php// Precision depends on your precision directiveecho sqrt(9); // 3echo sqrt(10); // 3.16227766 ...?>`

• pow() - Exponential expression

User Contributed Notes
sqrt
wietse89 at gmail dot com
27-Nov-2009 08:15
```For the second square root this code will work too: Note that it doesn't return float values. <?php \$new = strlen(decbin(256)); echo \$new; //8 ?>```
17-Aug-2009 09:45
```My little function to get the x'th square root of a value <?php /* * Example: second square root of 256 = 8 [reverse: pow(2,8) = 256] */ function xsqrt(\$x, \$value) {     \$count = 0;     do{         \$value=\$value/\$x;         \$count++;     }while(\$value>=\$x);     return \$count; } /* Example ip subnet: */ \$net_size = 256; \$subnet = 32 - xsqrt(2, \$net_size); echo '/' . \$subnet; /* returns: /24 */ ?>```
29-Mar-2006 08:03
```A much easier way to find perfect squares: This method uses integer roots to find perfect squares instead of integer squares to find integer roots. <? # initial value \$i = 0; #set any limit you want \$setSomeLimit = 10000; # do it! .... do it! ... do it! for (\$n = 1; \$n < sqrt(\$setSomeLimit; \$n++) {     // Find the square     \$s= \$n * \$n;     print "<br>perfect_square_root is of \$s is \$n"; } ?>```
php NOSPAM at primezero dot com
13-Jul-2005 02:15
```creating perfect squares... (no decimals) <? # initial value \$i = 0; #set any limit you want \$setSomeLimit = 10000; # do it! .... do it! ... do it! do {    # find the square root    \$sqRoot  = sqrt(\$i);       # not a decimal? that it is a perfect square! ^_^    if ( ereg ("^[0-9]{1,12}\$", \$sqRoot)) {           # suppose that the_square_root = teh_square_root        print "<br>perfect_square_root is of \$i is \$sqRoot";    } \$i++; # next!! # keeps running until it reaches the limit } while (\$i < \$setSomeLimit); ?>```
btharper1221 at gmail dot com
15-May-2005 03:48
```this is something you can use if you need an exact answer to a root problem, this includes an echo outside of the function to show how it works, it will return it such as \$ret is the number still part of the root (this is the exactness part of it) \$ret is the number of roots and \$ret is 1 or 0, 1 being that there should be an i following the number of roots (imaginary) <?php function newrt(\$val,\$rt){ \$i = 0; if((\$rt % 2 == 0) && (\$val < 1)){ \$i = 1; \$val = (-\$val); } \$c = 1; if((\$rt % 2 != 0) && (\$val < 0)){ \$c = -\$c; \$val = -\$val; } for(\$d = 2; pow(\$d,\$rt) <= abs(\$val); \$d++){ if(\$val % (pow(\$d,\$rt)) == 0){ \$val = (\$val/(pow(\$d,\$rt))); \$c = (\$c*\$d); \$d--; } } \$ret = \$val; \$ret = \$c; \$ret = \$i; return \$ret; }//end function newrt \$ret = newrt(\$num,\$num2); if(\$ret != 1){ if(\$ret == 0) echo \$ret." roots of ".\$ret; if(\$ret == 1) echo \$ret."<b><i>i</i></b> roots of ".\$ret; }elseif(\$ret == 1){ if(\$ret == 0) echo \$ret; if(\$ret == 1) echo "\$ret<b><i>i</i></b>"; } ?>```
chris DOT rutledge AT gmail DOT com
31-Mar-2005 10:24
```Just a note to say you can take the square root of a negative number - it returns an imaginary number. One might do it like this //take initial value of \$x \$abs_x = abs(\$x); \$answer = sqrt(\$abs_x); echo \$answer; if (\$x < 0) echo"<b><i>i</i></b>";```
jouhni at web dot de
17-Feb-2005 07:46
```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```
php user
13-May-2004 07:25
```How to calculate triangle's area if you haven't height measure. You need only sides' measure. it would have to work. (formula of erone) \$s1 = side 1 \$s2 = side 2 \$s3 = side 3 <? function area(\$s1,\$s2,\$s3) { \$calc1 = (\$s1+\$s2+\$s3)/2; \$calc2 = \$p*(\$p-\$s1)*(\$p-\$s2)*(\$p-\$s3); \$result = round(sqrt(\$p),2); return \$result; } ?> example of I use: <? //This will make to return the area of a triangle with sides of 3,4,5 \$area = area(3,4,5); echo \$area; ?>```
bishop
18-Jul-2003 05:09
```Compute a triangle's area: function triangleArea(\$a, \$b /* ... */) {     if (func_num_args() === 3) {         \$s = .5 * (\$a + \$b + (\$c = func_get_arg(2)));         return sqrt(\$s * (\$s-\$a) * (\$s-\$b) * (\$s-\$c));     } else {         return (.5 * \$a * \$b);     } } With 2 args, parameters are triangle's base and height.  With 3 args, parameters are the lengths of each side.  Argument order is not important. Either way, you get the area.```
tcn at pandora dot be
13-Nov-2002 08:37
```Checking if the square you want to take from a number is valid or not (you can't take the root of a negative number) if (\$i<0)  {   echo "Error! The number you specified can't be rooted! It's negative!   }   else   {   echo "The square root of your number is ".sqrt(\$i);   }```
morvandiumNOSPAM at yahoo dot com
05-Nov-2001 12:44
```I find this useful for any grid system where distances need to be computed (maps and graphs, mostly). Just use the distance between points formula (pseudo-code): sqrt((x2-x1)^2+(y2-y1)^2) to find the distance between two points.```