log

#include<stdio.h>
#include<math.h>
 
main()
{
   double number, result;
 
   printf("Enter a number to calculate it's natural log (base is e) ");
   scanf("%lf",&number);
 
   result = log(number);
 
   printf("Natural log of %lf = %lf", number, result);
 
   return 0;
}