math.h included, but fmod not available

[jamadagni]

I wrote a program to test my understanding of fmod:

#include <stdio.h>
#include <math.h>
 
int main(void) {
	double a = 259192.42201;
	double b = 24.10501259;
	printf("%11.10f", fmod(a,b));
}

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

int main(void) {
	double a = 259192.42201;
	double b = 24.10501259;
	printf("%11.10f", fmod(a,b));
}

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but I get the error:

samjnaa@linux:~/bin/learning> gcc fmod.c -o fmod
/tmp/ccK9XIYg.o: In function `main':
fmod.c.text+0x49): undefined reference to `fmod'
collect2: ld returned 1 exit status

and sure enough /usr/include/math.h has no reference to fmod -- what is this, GCC libraries are useless? Then how do I implement a modulus function? My GCC version is 4.0.2_20050901-3 and I have cpp, libgcc of same version, glibc 2.3.5-40 etc. Please help. Thanks.