9.2. Tangent Lines http://www.ck12.org
- Find the distance between the centers of the two circles. Reduce all radicals.
- IfDandCare the centers andAEis tangent to both circles, findDC.
Answers:
- 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.- 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.