Counting Perpendicular Line Pairs: Geometric Diagram Analysis

Let's remember that perpendicular lines are lines that form a right angle of 90 degrees between them.

Let's draw straight lines extending from each of the four vertices of the shape to examine whether the angles are right angles.

The drawing will look like this:

From the drawing, we can see that angles DAB+CBA are greater than 90 degrees, while angles ADC+DCB are less than 90 degrees.

Since no right angles are marked in the drawing, there are 0 pairs of perpendicular lines in the drawing.