10.1 CIRCLES AND CIRCUMFERENCES Ms. Andrejko

VOCABULARY Radius- a segment with endpoints at the

center and on the circle Chord- segment with both endpoints on the

circle Diameter- chord that passes through the

center and has endpoints on the circle Circle- the set of all points in a plane

equidistant from a given point called the center of a circle

Diameter (chord)

chord

radi

us center

MORE VOCAB…. Congruent circles- two circles are

congruent circles if and only if they have congruent radii

Concentric circles- coplanar circles that have the same center

EVEN MORE VOCABULARY A polygon is inscribed in a circle if all of its

vertices lie on the circle A circle is circumscribed about a polygon if

it contains all vertices of the polygon

Circumference:

C = πd

EXAMPLES

1. Name the circle.

2. Name a radius.

3. Name a chord.

PRACTICE

1. Name the circle.

2. Name a radius.

3. Name a chord.

EXAMPLES The diameters of circle L and circle M are 20

and 13 units, respectively, and QR = 4.

4. LQ=

5. RM=

PRACTICE The diameters of ⊙F and ⊙G are 5 and 6

units, respectively. Find each measure. 4. BF=

5. AB=

EXAMPLES Find the diameter, radius, and circumference

of a circle with the given information. 6. r = 21 ft

7. d = 18 cm

8. C = 6π m

PRACTICE Find the diameter, radius, and circumference

of a circle with the given information. 6. r = 17 ft

7. d = 26 cm

8. C = 22π m

EXAMPLES Find the circumference:

9. 10.

PRACTICE Find the circumference:

9. 10.