Area of largest triangle that can be inscribed within a rectangle in C Program?

Suppose one rectangle is given. We know the length L and breadth B of it. We have to find the area of largest triangle that can be inscribed within that rectangle −

The largest triangle will always be the half of the rectangle. So it will be

Example

#include <iostream>
#include <cmath>
using namespace std;
float area(float l, float b) {
   if (l < 0 || b < 0 ) //if the valuse are negative it is invalid
      return -1;
   float area = (l*b)/2;
   return area;
}
int main() {
   float a = 10, b = 8;
   cout << "Area : " << area(a, b);
}

Output

Area : 40