pi in c 2b 2b

1#define _USE_MATH_DEFINES // must include this!
2 
3#include <cmath>
4#include <iostream>
5 
6int main() { 
7  // M_PI = 3.14159265358979323846;
8  std::cout << M_PI << " " << M_E << " " << M_SQRT2 << endl;
9  return 0;
10}

1const float pi = 2 * acos(0.0f);

1typedef long double ld;
2const ld pi = 3.1415926535897932384626433832795;