Parallelogram in Railing

I noticed that the railing next to some stairs formed a parallelogram.

This parallelogram can be proved as a parallelogram since opposite angles are congruent.

If you draw a line from angle A to angle C, you can show theorem 5-11 which states that the segment that joins the midpoints of two sides of a triangle is 1. parallel to the third side and 2. half as long as the third side.

In the diagram this theorem is proved because 1. EF is parallel to BA which is shown by corresponding angles being congruent and 2. EF=15.60cm which is half as long as the 31.20cm length of BA.

Finally,  the area of a parallelogram is bh.  To find the height I drew an altitude from angle C down and used  sin of angle B

(∼NW5)