CK12 - Geometry

Let’s labelthe diagramand drawa line segmentthat joinsthe centersof the two circles.Also drawthe

segment perpendicularthe radius

Since is tangentto both circles, is perpendicularto both radii: and.

We can see that is a rectangle,therefore in.

This meansthat in in in.

is a right trianglewith in and in. We can applythe PythagoreanTheorem

to find the missingside,.

The distancebetweenthe centersisapproximately inches.

CommonInternalTangents

Hereis an examplein whichyou mightencounterthe use of commoninternaltangents.

Example 2

is tangentto both circles.Find the valueof and the distancebetweenthe centersof the circles.