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# Circles - PowerPoint PPT Presentation

Circles. Honors Math – Grade 4. A. Circle. A circle is a plane figure. All the points on a circle are the same distance from a given point, called the center. Point A is the center of the circle. Circle A. A circle is named by its center point. C. E. B. D. G. F.

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## PowerPoint Slideshow about 'Circles' - manning

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Presentation Transcript

### Circles

Circle

• A circle is a plane figure.

• All the points on a circle are the same distance from a given point, called the center.

• Point A is the center of the circle

Circle A

A circle is named by its center point.

E

B

D

G

F

The Parts of Circle B

• All the line segments in Circle B have special names.

• Can you name any points on the circle?

• E, C, D, F, G

E

B

D

G

F

• A radius is a line segment with endpoints at the centerof the circle and on the circle.

E

B

D

G

F

Diameter

• A diameter is a line segment that passes through the center of the circle and has bothendpoints on the circle.

• is a diameter.

The length of the diameter is always equal to twice the length of the radius.

12 cm

If BE measures 6 cm, how long is CD?

E

B

D

G

F

Chord

• A chord is a line segment with both endpoints on the circle.

• is a chord.

• Are there any other chords in Circle B?

• Line segment CD

A diameter is a special chord.

• A simple closed curve is a path that begins and ends at the same point and does not cross itself.

Simple Closed Curves

Not simple closed curves

T

V

S

R

X

W

Q

Practice

• Name the circle and its center.

• How many diameters are shown? Name the diameters.

• Is TR a radius? Explain why or why not?

• Is VX a radius? Explain why or why not?

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• Circle V. The center is point V.

• There are 3 diameters. PQ, RS, TW

• TS is not a radius because it does not have an endpoint at the center of the circle and it is a chord.

• VX is a radius because its endpoints are the center point V and point X on the circle.

• There are 7 radii. VP, VS, VW, VQ, VX, VR, VT