You are building a geometry calculation tool that can compute the area of different shapes. You will implement function overloading so that the same function name calculateArea can handle rectangles, circles, and triangles.

1. Rectangle Area Function

   • Declare a function calculateArea that takes two double parameters: length and width.
   • Inside the function, calculate the area by multiplying length by width.
   • Return the calculated area.

2. Circle Area Function

   • Overload the calculateArea function to take one double parameter: radius.
   • Calculate the area using the formula PI multiplied by radius squared, using the pow function to raise radius to the power of 2.
   • Return the calculated area.

3. Triangle Area Function

   • Overload the calculateArea function to take three double parameters: a, b, and c.
   • Compute the semi-perimeter s = (a + b + c) / 2.
   • Use Heron's formula: sqrt(s * (s - a) * (s - b) * (s - c)) to calculate the area.
   • Return the calculated area.

Do not modify the value of the PI variable.

Example

calculateArea(4, 6) → 24 (rectangle)
calculateArea(3) → 28.27431 (circle)
calculateArea(5, 4, 6) → 9.92157 (triangle)