Xcode Mac OS X 10.7.5 doesn't compile file with math header

Question

Hello!
I've written a simple program (just at the beginning of my programming path). A few people have tested it on their machines, and it works: their Xcode compiles the program. My Xcode does not.
Here is the program.
#include <math.h>
#include <stdio.h>
int main (void)
   float x = 2.55, y1, y2 ;
   int   i = 3, z = 2 ;
         y1 = pow( x, i ) ;
         y2 = pow( x, z ) ;
   float result ;
   result = 3 * y1 - 5 * y2 + 6 ;
   printf ("If x equals %f, then the given polynomial equals %f\n", x, result) ;
   return 0 ;
Here is what I get after trying to compile:
alla [11:41 AM]
95-28-37-123:~ Alla$ gcc Prog3task6add.c -o Prog3task6add
Undefined symbols for architecture x86_64:
"_main", referenced from:
     start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
Besides this program, programs with simple #include <stdio.h> header work perfectly.
I use Mac OS X 10.7.5 Scode 4.6.3
Thank you very much!

Answer 1

Hello!
I have tried to use the flag in the program below. Although the program has no reference to math.h library, it returns the same error message.
/* Program to calculate the average of a set of grades and count the nuber of failing test grades */
#include <stdio.h>
int main (void)
    int number_of_grades, i, grade;
    int grade_total = 0, failure_count = 0 ;
    float average ;
    printf ("How many grades will you be entering? ") ;
    scanf ("%i", &number_of_grades) ;
    for ( i = 1; i <= number_of_grades; ++i )
        printf ("Enter grade #%i: ", i) ;
        scant ("%i", &grade) ;
        grade_total += grade ;
        if ( grade < 65 ) ;
        ++failure_count ;
    average = (float) grade_total / number_of_grades ;
    printf ("\nGrade average = %.2f\n", average) ; // Precision to two decimal points
    printf ("Number of failures = %i\n", failure_count) ;
    return 0 ;
Error message:
Undefined symbols for architecture x86_64:
  "_scant", referenced from:
      _main in cchfawYD.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
I would be grateful for ideas on how to solve this. Can it be due to the older version of git?
Thank you so much!