Pre-Calc Exam Notes 64

Pre-Calc Exam Notes 64 - 64 Chapter 2 General Triangles 2.5...

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64 Chapter 2 General Triangles §2.5 Example 2.19 Find the radius r of the inscribed circle for the triangle ABC from Example 2.6 in Section 2.2: a = 2, b = 3, and c = 4. Draw the circle. O A B C Figure 2.5.8 Solution: Using Theorem 2.11 with s = 1 2 ( a + b + c ) = 1 2 (2 + 3 + 4) = 9 2 , we have r = r ( s a )( s b )( s c ) s = R ± ± ² ( 9 2 2 ) ( 9 2 3 ) ( 9 2 4 ) 9 2 = ³ 5 12 . Figure 2.5.8 shows how to draw the inscribed circle: draw the bisectors of A and B , then at their intersection use a compass to draw a circle of radius r = r 5/12 0.645. Exercises For Exercises 1-6, ±nd the radii R and r of the circumscribed and inscribed circles, respectively, of the triangle ABC . 1. a = 2, b = 4, c = 5 2. a = 6, b = 8, c = 8 3. a = 5, b = 7, C = 40 4. A = 170 , b = 100, c = 300 5. a = 10, b = 11, c = 20.5 6. a = 5, b = 12, c = 13 For Exercises 7 and 8, draw the triangle ABC
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This note was uploaded on 01/21/2012 for the course MAC 1130 taught by Professor Dr.cheun during the Fall '11 term at FSU.

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