The third root of a number

[dwks]

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:

#include <math.h>

sqrt(sqrt(81));

But that only works for multiples of two.

[Dave_Sinkula]

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.

pow(x, 1.0 / n);

[ILoveVectors]

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

[Tonto]

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

#include <math.h>
#include <stdio.h>

int main ()
{
	printf("%2.2f", pow(125, 1.0 / 3.0));
	return 0;
}

Retuns a clean 5.

[grumpy]

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

#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;
}

[dwks]

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