CIRCLES CIRCLES A circle is a plane figure

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CIRCLES

CIRCLES

CIRCLES • A circle is a plane figure. All points of the circle are

CIRCLES • A circle is a plane figure. All points of the circle are the same distance from a given point, called center. • This circle is called circle A since the center is at point A. • every circle has a radius, a diameter, a circumference, and an area.

A chord Is a line segment with its endpoints on the circle. LK and

A chord Is a line segment with its endpoints on the circle. LK and MN are chords of circle C. L L . K C M N

Radius: The radius of a circle is the line segment with one end point

Radius: The radius of a circle is the line segment with one end point at the center of the circle and the other end point on the circle. It's the same distance anywhere on the circle, because the circle has radial symmetry. So it doesn't matter where you measure the radius on the circle, and if you know one radius measurement for a circle, then you know all of them. AB is radious of circle A A B

Diameter. • A diameter is a chord that runs through the center point of

Diameter. • A diameter is a chord that runs through the center point of the circle and touching two points on its edge. • The diameter is always equal to twice the radius of the circle, because the radius starts from the center of the circle and goes straight to the edge. • CB is the diameter of circle A. B A C

Activity Use the circle at the right. 1. Name the circle and its center.

Activity Use the circle at the right. 1. Name the circle and its center. 2. Name 5 points of the circle 3. How many chords of the circle are shown? Name them. 4. Is XY a diameter of the circle? Explain why or why not 5. How many diameters of the circle are shown? Name them 6. How many radii of the circle are shown? Name them. . . O X . . O . Z. Y

Write the correct letter 1. Chord ( a. A chord that passes through the

Write the correct letter 1. Chord ( a. A chord that passes through the center of the circle 2. Radius ( ) b. a point that names the circle 3. Diameter ( ) c. A line segment joining any two points on the 4. Center ( ) circle d. A line segment drawn from the center of the circle to any point of the circle )

Constructing a circle A compass can be used to construct a circle. The compass

Constructing a circle A compass can be used to construct a circle. The compass tip marks the center of the circle. The distance the compass is open is the radius of the circle. A ruler or straightedge is used to draw the parts of the circle. Point for center radius

Activity 2. Use a compass to construct a circle. Then do the following: a.

Activity 2. Use a compass to construct a circle. Then do the following: a. Label the center point, X. b. Draw chord MN. c. Draw diameter VT. d. Draw radius XR