using System;

public class Program

{

    static double ScaleFOVByWidthRatio(double ratio)

    {

        ratio /= (4.0 / 3.0);

        var halfAngleRadians = 90 * (0.5 * Math.PI / 180.0);

        var t = Math.Tan(halfAngleRadians);

        t *= ratio;

        var retDegrees = (180.0f / Math.PI) * Math.Atan(t);

        return retDegrees * 2.0;

    }

    public static void Main()

    {

        Console.WriteLine($"16/3 = {ScaleFOVByWidthRatio(16.0/3.0):####}°");

        Console.WriteLine($"16/9 = {ScaleFOVByWidthRatio(16.0/9.0):####}°");

        Console.WriteLine($"16/10 = {ScaleFOVByWidthRatio(16.0/10.0):####}°");

        Console.WriteLine($"4/3 = {ScaleFOVByWidthRatio(4.0/3.0):####}°");

        Console.WriteLine($"5/4 = {ScaleFOVByWidthRatio(5.0/4.0):####}°");

    }

}