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js_student20
·
How to correctly use the PI constant (π) in C++?
Hi! I just started learning C++ and am trying to write a program to calculate the area of a circle. I need to use the number π (pi), but I don't understand how to properly declare it or where to get it.
I tried writing this:
```cpp
#include
using namespace std;
int main() {
double radius = 5.0;
double area = 3.14159265359 * radius * radius; // just hardcoded the number
cout << "Area: " << area << endl;
return 0;
}
```
But this looks hacky. I heard there is a constant M_PI, but when I write `#define _USE_MATH_DEFINES` or include ``, it doesn't work — the compiler complains that M_PI is not declared.
Tell me, how to correctly use PI in C++? Is there a standard way? Or do I always have to declare `const double PI = 3.141592653589793;` myself? Thanks in advance!
P.S. I'm using Visual Studio 2022, if that matters.
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Correct ways to use the π constant in C++
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