Question

In real world cube root for a negative number should exist:
cuberoot(-1)=-1, that means (-1)*(-1)*(-1)=-1
or
cuberoot(-27)=-3, that means (-3)*(-3)*(-3)=-27

But when I calculate cube root of a negative number in C using pow function, I get nan (not a number)

double cuber;
cuber=pow((-27.),(1./3.));
printf("cuber=%f\n",cuber);

output: cuber=nan

Is there any way to calculate cube root of a negative number in C?

Answer 1

7.12.7.1 The cbrt functions

Synopsis

#include <math.h>
double cbrt(double x);
float cbrtf(float x);
long double cbrtl(long double x);

Description

The cbrt functions compute the real cube root of x.

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If you’re curious, pow can’t be used to compute cube roots because one-third is not expressible as a floating-point number. You’re actually asking pow to raise -27.0 to a rational power very nearly equal to 1/3; there is no real result that would be appropriate.