Geometry: An Interactive Journey to Mastery

Lesson 19: The Geometry of a Circle

 Tangent circles with centers A and B have radii of 8

and 6, respectively.

Find the length of the common tangent segment shown

in )LJXUH.

 Explain why the two chords shown in )LJXUH must

be parallel.

 Find the measure of angle a in the diagram in )LJXUH.

 Prove that ab = cdͼ௘6HH)LJXUH௘ͽ

 The four corners of a parallelogram happen to lie on a circle.

Explain why that parallelogram must be a rectangle.

The circle with center P of radius 25 and the circle

with center Q of radius 29 intersect at A and B.

ͼ௘6HH)LJXUH௘ͽ

If PQ = 36, what’s AB?

A B

Figure 19.17

68° 68°

Figure 19.18

Figure 19.19

130°

a 40°

A B

C

D

Figure 19.20

ac

d b

Figure 19.21

A

B

P Q