#include <stdio.h>
#include <dlfcn.h>

void main(void)
{
	void *handle;
	double (*cosine)(double);
	char *error;

	handle = dlopen("/usr/lib/libm.so", RTLD_LAZY);
	if (! handle) {
		fprintf(stderr, "%s\n", dlerror());
		exit(1);
	}
	cosine= dlsym(handle, "cos");
	if ((error = dlerror()) != NULL) {
		fprintf(stderr, "%s\n", error);
		exit(1);
	}

	printf("%f\n", (*cosine)(2.0));

	dlclose(handle);
}
.