Calculate the square root of a number

### Prototypes

#include <math.h>
double sqrt(double x);
float sqrtf(float x);
long double sqrtl(long double x);

### Description

Computes the square root of a number. To those of you who don't know
what a square root is, I'm not going to explain. Suffice it to say, the
square root of a number delivers a value that when squared (multiplied
by itself) results in the original number.

Ok, fine—I did explain it after all, but only because I wanted
to show off. It's not like I'm giving you examples or anything, such as
the square root of nine is three, because when you multiply three by
three you get nine, or anything like that. No examples. I hate
examples!

And I suppose you wanted some actual practical information here as
well. You can see the usual trio of functions here—they all
compute square root, but they take different types as arguments. Pretty
straightforward, really.

### Return Value

Returns (and I know this must be something of a surprise to you) the
square root of `x`. If you try to be smart and pass a negative
number in for `x`, the global variable `errno` will be
set to `EDOM` (which stands for DOMain Error, not some kind of
cheese.)

### Example

// example usage of sqrt()
float something = 10;
double x1 = 8.2, y1 = -5.4;
double x2 = 3.8, y2 = 34.9;
double dx, dy;
printf("square root of 10 is %.2f\n", sqrtf(something));
dx = x2 - x1;
dy = y2 - y1;
printf("distance between points (x1, y1) and (x2, y2): %.2f\n",
sqrt(dx*dx + dy*dy));

And the output is:

square root of 10 is 3.16
distance between points (x1, y1) and (x2, y2): 40.54

### See Also

`hypot()`