Geometry Problem 1378: Parallelogram, Diagonal perpendicular to a side,
Distances from a Point to Vertices, Measurement.
Proposition
In the figure below,
ABCD is a parallelogram so that BD is perpendicular to AB. F is any point,
FA = a, FB = b, FC = c, FD = d, and AB = e. Prove that a2 + c2 = b2 + d2
+2(e2)