## Elementary Geometry for College Students (7th Edition)

Published by Cengage

# Chapter 8 - Section 8.2 - Perimeter and Area of Polygons - Exercises - Page 370: 10

#### Answer

84 $cm^{2}$

#### Work Step by Step

Given sides of a triangle 10 cm, 17 cm, 21 cm Using Heron's formula if three sides of a triangle have length a,b,c then area A of a triangle is A = $\sqrt s(s-a)(s-b)(s-c)$ where s = $\frac{a+b+c}{2}$ Lets take a=10 b=17 and c=21 s = $\frac{10+17+21}{2}$ = 24 cm A = $\sqrt 24(24-10)(24-17)(24-21)$ =$\sqrt 24*14*7*3$ =84 $cm^{2}$

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