# Euler Line
Let(A = [0, 0], B = [x1, 0], C = [x2, x3], X = [x4, x5], Y = [x6, x7],
    Z = [x8, x9]):
EulerLine := Theorem([arbitrary(A,B,C), centroid(A,B,C,X),
                  circumcenter(A,B,C,Y), orthocenter(A,B,C,Z)],
                  collinear(X,Y,Z), [x4,x5,x6,x7,x8,x9]);
