# Thread: The third root of a number

1. ## The third root of a number

I was wondering how to calculate the third square root of a number. Or the nth square root of a number. Is there a function for it?

I know you can calculate the fourth square root like this:
Code:
```#include <math.h>

sqrt(sqrt(81));```
But that only works for multiples of two.

2. I don't know if I understand what you mean by "third" and "fourth" square root. If you just mean the third root, 4th root, nth root, then I'd say use pow.
Code:
`pow(x, 1.0 / n);`

3. he means, the cubed root, (when he talking about third)

8 * 8 * 8 = 512 // he want to know how to find the 8

3 * 3 * 3 = 27 // he want to know how to find the 3

or if this came up

5 * 5 * 5 * 5 = 625 // he want to know how to find the 5

4. Of course he does. And of course, square roots, cube roots, etc. are really just fractional exponents. Thus:

Code:
```#include <math.h>
#include <stdio.h>

int main ()
{
printf("%2.2f", pow(125, 1.0 / 3.0));
return 0;
}```
Retuns a clean 5.

5. An alternative, which has both advantages and disadvantages over using pow(), is

Code:
```#include <math.h>
#include <stdio.h>

int main ()
{
double x = 125.0;
int n;
printf("%2.2f", exp(log(x)/n));   /* x an n must both be positive */
return 0;
}```

6. Okay, thanks. I don't know why I never thought of the pow() version . . . .