Big Ideas Math Geometry, 2014
BI
Big Ideas Math Geometry, 2014 View details
1. Lines and Segments That Intersect Circles
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Exercise 48 Page 536

Start with evaluating the area of a triangle.

units

Practice makes perfect

Let's take a look at the given diagram. We are given that and so the drawn triangle is isosceles. Additionally we know that all three segments are tangent to

First let's evaluate the height of the triangle To do this let's recall that the height in an isosceles triangle bisects the base.

Let's write an equation for using the Pythagorean Theorem. Notice that since represents the height, we will consider only positive case when taking a square root of
Solve for
The height of the triangle is approximately units. Using this value, we can evaluate the area of a triangle.
The area of the triangle is square units. Next let's recall that tangent segments are perpendicular to the radii at the tangency points. Let's call the radius of the circle

If we connect each vertex with the center of a triangle, then we have three triangles each with the height of

Notice that the sum of the areas of these three triangles needs to be equal to the area of We will use the formula for the area of a triangle to write an equation and solve for
Let's solve the equation to find the radius.
Solve for
The radius of the circle is approximately units.