/// <summary>
/// Gets the name of a triangle with the given stats.
/// </summary>
/// <param name="stats">The stats object of the triangle.</param>
/// <returns>The name of the triangle with the given stats.</returns>
public static string GetTriangleName(TriangleStats stats)
{
var result = "";
switch (stats.Angle)
{
case TriangleAngle.Acute:
result = "acute";
break;
case TriangleAngle.Right:
result = "right";
break;
case TriangleAngle.Obtuse:
result = "obtuse";
break;
}
switch (stats.Type)
{
case TriangleType.Equilateral:
// all equilateral triangles are also acute triangles, so no need to keep it in the name
result = "equilateral";
break;
case TriangleType.Isosceles:
result += " isosceles";
break;
case TriangleType.Scalene:
result += " scalene";
break;
}
return(result);
}
/// <summary>
/// Calculates the stats of a triangle with the given side lengths.
/// Throws an exception if the sides do not create a valid triangle (triangles with zero area are allowed).
/// </summary>
/// <param name="sideA">The length of side A of the triangle.</param>
/// <param name="sideB">The length of side B of the triangle.</param>
/// <param name="sideC">The length of side C of the triangle.</param>
/// <returns>An object containing the triangle's stats.</returns>
public static TriangleStats GetTriangleStats(double sideA, double sideB, double sideC)
{
if (sideA < 0)
{
throw new ArgumentException(ERR_NEGATIVE_LENGTH, "sideA");
}
if (sideB < 0)
{
throw new ArgumentException(ERR_NEGATIVE_LENGTH, "sideB");
}
if (sideC < 0)
{
throw new ArgumentException(ERR_NEGATIVE_LENGTH, "sideC");
}
if (sideC > sideA + sideB || sideA > sideB + sideC || sideB > sideC + sideA)
{
throw new InvalidTriangleException("No side's length can be greater than the sum of the other two.");
}
var info = new TriangleStats();
// check side lengths
var AeqB = sideA == sideB;
var BeqC = sideB == sideC;
var CeqA = sideC == sideA;
if (AeqB && BeqC)
{
info.Type = TriangleType.Equilateral;
}
else if (AeqB || BeqC || CeqA)
{
info.Type = TriangleType.Isosceles;
}
else
{
info.Type = TriangleType.Scalene;
}
// check angles
// uses cosine rule to calculate angles A and B, and subtract both from 180 degrees to find C
var angA = Math.Acos((Math.Pow(sideB, 2) + Math.Pow(sideC, 2) - Math.Pow(sideA, 2)) / (2 * sideB * sideC));
var angB = Math.Acos((Math.Pow(sideA, 2) + Math.Pow(sideC, 2) - Math.Pow(sideB, 2)) / (2 * sideA * sideC));
var angC = Math.PI - angA - angB;
// allow a small margin of error to account for floating-point innacuracy
if (Math.Abs(angA - RIGHT_ANGLE) < FP_MARGIN || Math.Abs(angB - RIGHT_ANGLE) < FP_MARGIN || Math.Abs(angC - RIGHT_ANGLE) < FP_MARGIN)
{
info.Angle = TriangleAngle.Right;
}
else if (angA > RIGHT_ANGLE || angB > RIGHT_ANGLE || angC > RIGHT_ANGLE)
{
info.Angle = TriangleAngle.Obtuse;
}
else
{
info.Angle = TriangleAngle.Acute;
}
return(info);
}
protected string GetTriangleMessage(TriangleStats info)
{
return(string.Format(VALID_RESULT_TEXT, TriangleChecker.GetTriangleName(info)));
}
