http://www.ck12.org Chapter 9. Circles
DC=AC−AD
DC=
√
89 − 5 ≈ 4. 43
Example 5:Determine if the triangle below is a right triangle. Explain why or why not.
Solution:To determine if the triangle is a right triangle, use the Pythagorean Theorem. 4
√
10 is the longest length,
so we will set it equal tocin the formula.
82 + 102?
(
4
√
10
) 2
64 + 1006 = 160
4 ABCis not a right triangle. And, from the converse of the Tangent to a Circle Theorem,CBis not tangent to
⊙
A.
Example 6:Find the distance between the centers of the two circles. Reduce all radicals.
Solution:The distance between the two circles isAB. They are not tangent, however,AD⊥DCandDC⊥CB. Let’s
addBE, such thatEDCBis a rectangle. Then, use the Pythagorean Theorem to findAB.