Answer:
Perpendicular
Step-by-step explanation:
Calculate the slopes m of the segments using the slope formula.
m = 
Parallel lines have equal slopes
The product of the slopes of perpendicular lines equals - 1
(x₁, y₁ ) = A(0, 0) and (x₂, y₂ ) = B(e, f)
=
= 
Repeat with (x₁, y₁ ) = C(0, e) and (x₂, y₂ ) = D(f, 0)
=
= - 
Thus AB and CD are perpendicular since
× -
= - 1