In the triangle ABC AC = BC = 20 inches and AB = 10 inches. Circle is inscribed in the triangle, what is the radius of the circle...see attached...#71

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- Feb 12th 2010, 02:22 PM #1

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- Feb 12th 2010, 02:35 PM #2

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- Feb 12th 2010, 02:40 PM #3

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- Feb 12th 2010, 05:18 PM #7

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- Feb 13th 2010, 01:39 AM #8
1. You are dealing with 2 right triangles. (see attachment)

2. Grey triangle:

3. The right triangle at the top of the grey triangle:

4. Calculate h from 2. and plug in this term into the equation in 3. Solve for r.

__Spoiler__:

Second attempt: The 2 right triangles are similar. So use proportions:

First calculate h, then r using the proportion.