Next, let’s learn about parallelograms. 3 Find the Perimeter and Area of a Parallelogram Definition A parallelogram is a four-sided fi gure whose opposite sides are parallel and the same length. Here are two examples of parallelograms. 15 in. 15 in. 8 in. 8 in. A B D C The opposite sides are the same length, and they are parallel. AD 0 0 BC (AD is parallel to BC) and AB 0 0 DC (AB is parallel to DC) Opposite sides are the same length, as indicated by the hash marks “0” and “0 0”. Note Rectangles and squares are also parallelograms. 3 cm 5 cm 5 cm 3 cm mi 2 3 mi 2 3 To fi nd the perimeter of a parallelogram, we add the lengths of the four sides. To fi nd the area of a parallelogram, we use the following formula. Formula Area of a Parallelogram The area, A, of a parallelogram is Area base height or A bh where b the length of the base and h the height. Notice that the base is the side that forms a right angle with the height. height, h base, b The derivation of the formula of the area of a parallelogram can be found in Appendix B.3 www.mhhe.com/messersmith SECTION 4.2 Rectangles, Squares, Parallelograms, and Trapezoids 299
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