Problem 235.
Parallelogram, Transversal line, Perpendicular lines,
Measurement

The figure shows a parallelogram ABCD,
A'C' is a transversal line. If a, b, c, and d are the perpendiculars
drawn from A, B, C, and D to the line A'C', respectively,
prove that: a + b = c + d.
View or post a solution.