Why is the constant π not fully deduced?

Question

C++ / C#

Here is the complete code ->

#include <stdio.h>
#include <math.h>
#define PI M_PI
 //Compiler version gcc 6.3.0

 int main()
 {   
 	printf("%f", PI);
 	return 0;
 }

The result is 3.141593.

Answer 1

Why is the constant π not fully deduced?

An irrational number, on the other hand, cannot be deduced completely with the current level of technology.