🚀 go-pugleaf

I installed gcc together with Linux from the Linux Slackware package. The
bin, include and lib directories are directly under /usr, which is different
from what you described for a separate installation in which they should be
under /usr/local. Anyway, gcc generally works except it can not find the
intrinsic functions (like sin, sqrt, etc.) that need <math.h>. My test
program is like this:

#include <stdio.h>
#include <math.h>
main()
{
 double x;
 x=sin(3.14159/6.0);
 printf("x=%f\n",x);
}

when I used gcc to compile and link the program, it gave me an error message:
/tmp/xxxxxxxx:   undefined reference to 'sin'
I checked /usr/include directory, both stdio.h and math.h are there! Do you
know what the problem is? Please help me.
Jian