Problem 171.
Trapezoid, Midpoints, Triangles, Areas.

In the figure below, ABCD is a
trapezoid with AD parallel to BC and E, F, and G midpoints of AB, BC, and
AD respectively. Lines EC, ED, and FG determine the shaded
regions of areas S, S1,
and S2.
Prove that S
= S1
+
S2.
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