The 25-Pin Lattice Geoboard
Fig. 18a
Let us project side BC on AC to obtain the length CD1.
Fig. 18b
Constructing a rectangle measuring AC by CD1, we obtain the rectangle d1. Hence a = b + c + 2d1 (Here a = 5 units of area, b = 2 units, c = 1 unit, d1 = 1 unit).
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