How can i write "" ln 3 "" on c++ ?

Hi.
-----
Thanks for reading ...

I want to write for example: ln 3

Is there is any command or function for it ...!

 

maybe you want this

Code:

#include<stdio.h>
#include<math.h>
int main(){
    double e = 2.718281828;
    double x = log(e);
    printf("%f",x);
    getchar();
    return 0;
}