Example of pow function that is built in function of library

#include<stdio.h>
#include<stdlib.h>
void line()
{
int i,j;
printf("\n");
for(i=1;i<=42;i++)
printf("=");
}
void header()
{
printf("\n");
printf("Built and Designed by Arslan Malik\n\n www.CworldbyAS.blogspot.com");
printf("\n");
}
int main()
{
line();
header();
line();

double a=2.5;
double b=3;
printf("%10.2f",pow(a,b));


return 0;
}