Area of Parallelogram

The area of a rectangle equals the product of its sides. The area of a parallelogram equals the product of one of its sides times the distance between that side and its parallel (and equal) mate.

It's customary to base a demonstration for the area of a parallelogram formula on Figure 1 below:

Area$(ABCD)$ = Area$(AFD)$ + Area$(DFBC)$

= Area$(BGC)$ + Area$(DFBC)$

= Area$(DFGC)$.

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