internal static T Determinant <T>(this Matrix3x3 <T> a)
where T : IComparable <T> =>
Operations.Add(
Operations.Add(
Operations.Multiply(a[0, 0], a.Cofactor(0, 0)),
Operations.Multiply(a[0, 1], a.Cofactor(0, 1))),
Operations.Multiply(a[0, 2], a.Cofactor(0, 2)));
public void TestCalculateDeterminantOf3x3Matrix()
{
var a = new Matrix3x3(
1, 2, 6,
-5, 8, -4,
2, 6, 4);
Assert.Equal(56, a.Cofactor(0, 0));
Assert.Equal(12, a.Cofactor(0, 1));
Assert.Equal(-46, a.Cofactor(0, 2));
Assert.Equal(-196, a.Determinant());
}
public void TestCalculateCofactorOf3x3Matrix()
{
var a = new Matrix3x3(
3, 5, 0,
2, -1, -7,
6, -1, 5);
Assert.Equal(-12, a.Minor(0, 0));
Assert.Equal(-12, a.Cofactor(0, 0));
Assert.Equal(25, a.Minor(1, 0));
Assert.Equal(-25, a.Cofactor(1, 0));
}
public void Determinate()
{
var matrix = new Matrix3x3(
1, 2, 6,
-5, 8, -4,
2, 6, 4);
Assert.Equal(56, Matrix3x3.Cofactor(matrix, 0, 0));
Assert.Equal(12, Matrix3x3.Cofactor(matrix, 0, 1));
Assert.Equal(-46, Matrix3x3.Cofactor(matrix, 0, 2));
Assert.Equal(-196, Matrix3x3.Determinate(matrix));
}
public void Cofactor()
{
var matrix = new Matrix3x3(
3, 5, 0,
2, -1, -7,
6, -1, 5);
Assert.Equal(-12, Matrix3x3.Minor(matrix, 0, 0));
Assert.Equal(-12, Matrix3x3.Cofactor(matrix, 0, 0));
Assert.Equal(25, Matrix3x3.Minor(matrix, 1, 0));
Assert.Equal(-25, Matrix3x3.Cofactor(matrix, 1, 0));
}
public void Cofactor_should_return_the_cofactor_of_the_matrix()
{
var matrix = new Matrix3x3(
3, 5, 0,
2, -1, -7,
6, -1, 5);
matrix.Cofactor(0, 0).Should().Be(-12);
matrix.Cofactor(0, 1).Should().Be(-52);
matrix.Cofactor(0, 2).Should().Be(4);
matrix.Cofactor(1, 0).Should().Be(-25);
matrix.Cofactor(1, 1).Should().Be(15);
matrix.Cofactor(1, 2).Should().Be(33);
matrix.Cofactor(2, 0).Should().Be(-35);
matrix.Cofactor(2, 1).Should().Be(21);
matrix.Cofactor(2, 2).Should().Be(-13);
}
internal static double Determinant(this Matrix3x3 a) => (a[0, 0] * a.Cofactor(0, 0)) + (a[0, 1] * a.Cofactor(0, 1)) + (a[0, 2] * a.Cofactor(0, 2));