find the surface area of a regular polygon inscribed in a cylinder in csharp

main.cs
public static double SurfaceAreaOfInscribedRegularPolygon(double numSides, double radius, double height)
{
    double apothem = radius * Math.Cos(Math.PI / numSides);
    double sideLength = 2 * radius * Math.Tan(Math.PI / numSides);

    double polygonArea = 0.5 * numSides * sideLength * apothem;

    double lateralArea = 2 * Math.PI * radius * height;

    double baseArea = numSides * Math.Pow(radius, 2) * Math.Tan(Math.PI / numSides);

    return lateralArea + 2 * polygonArea + 2 * baseArea;
}
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main.cs
double numSides = 6;  // hexagon
double radius = 2;
double height = 5;

double surfaceArea = SurfaceAreaOfInscribedRegularPolygon(numSides, radius, height);

Console.WriteLine("Surface area of inscribed regular polygon: {0}", surfaceArea);
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