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AMSCO'S Geometry. New York - Rye High School

AMSCO'S Geometry. New York - Rye High School

AMSCO'S Geometry. New York - Rye High School

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Surface Area of a Prism 443EXAMPLE 1The bases of a right prism are regular hexagons. The length of each side of abase is 5 centimeters and the height of the prism is 8 centimeters. Describe thenumber, shape, and size of the lateral sides.SolutionAnswerA hexagon has six sides. Because the base is a regularhexagon, it has six congruent sides, and therefore, theprism has six lateral sides. Since it is a right prism, thelateral sides are rectangles. The length of each of twoedges of a lateral side is the length of an edge of abase, 5 centimeters. The length of each of the othertwo edges of a lateral side is the height of the prism,8 centimeters.There are six lateral sides, each is a rectangle that is8 centimeters by 5 centimeters.8 cm5 cmEXAMPLE 2The bases of a right prism are equilateral triangles. The length of one edge of abase is 4 inches and the height of the prism is 5 inches.a. How many lateral sides does this prism have and what is their shape?b. What is the lateral area of the prism?Solutiona. Because this is a prism with a triangular base, the prism has three lateralsides. Because it is a right prism, the lateral sides are rectangles.b. For each rectangular side, the length of one pair of edges is the length of anedge of the base, 4 inches. The height of the prism, 5 inches, is the length ofa lateral edge. Therefore, the area of each lateral side is 4(5) or 20 squareinches. The lateral area of the prism is 3(20) 60 square inches.Answers a. 3 b. 60 square inchesEXAMPLE 3The lateral sides of a prism are five congruent rectangles.Prove that the bases are equilateral pentagons.ProofThe five lateral sides are congruent rectangles. Two parallelsides of each rectangle are lateral edges. The other twoparallel sides of each rectangle are edges of the bases.Each edge of a base is a side of a rectangle. Therefore, thebase has five sides. The corresponding sides of the congruentrectangles are congruent. Therefore, the edges of eachbase are congruent. The bases are equilateral pentagons.

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