 \vec{ AB}\;=\;-\vec{CD} 

 \vec{ BC }\;=\;-\vec{DA} 

A = (21.037000000000003, 3.378000000000002)
B = (28.635800000000003, 3.426400000000002)
u = Vector(A, B)
C = (26.603, -0.9779999999999985)
v = Vector(B, C)
a = Line(C, u)
b = Line(A, v)
D = Intersect(a, b)
w = Vector(C, D)
z = Vector(D, A)