log() : logarithm of x to the base e

log(x) 

Example

#include <stdio.h>
#include <math.h>
int main(void){
     double  x,ret;
     x=3.54;
     ret=log(x);
     printf("log(%.2f)=%.2f", x,ret);
     return 0;
}

log(3.54)= 1.26