# 4.1 Introduction To Circles Essay

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4.1 Introduction to Circles Name: ________________________ Math 2 Date: ________________________ Standard: Essential Question: Definition: A circle is the set of all points in a plane at a given distance from a given point. A. A circle is named by its center. The circle shown below has center C so it is called circle C. This is symbolized by writing [pic]C. B. Draw a line segment by connecting points C and D in the circle above. The segment you have drawn is called a radius. The plural of radius is radii. Name three other radii of the circle. Be sure to use the correct notation for a line segment: ______ , ______ , ______ Note: one endpoint of the radius is the center of the circle and the other endpoint is a point on the circle. Also, all radii of a circle are congruent. So, if AC = 2 cm, then CE = _____ cm. C. Now, make another segment by connecting points A and E. The segment you have drawn is called a chord. Name five other chords of the circle. ______ , ______ , ______ , ______ , ______ Note: both endpoints of a chord are points on the circle. Chords of a circle do not necessarily have the same length. D. If a chord passes through the center of a circle it is given a special name. It is called a diameter. Name the diameter pictured in [pic]C. _________ Now, draw that diameter. Note: a diameter is the longest chord of a circle. Its length is twice that of the radius. So, if AC = 2 cm, then AB = _____ cm. E. Next, draw a line passing through points B and F. The line you have drawn is called a tangent. A tangent lies in the plane of the circle and intersects the circle in only one point. The point of intersection is called the point of tangency. What is the point of tangency for [pic]? ________ F. Now, draw the line passing through points A and F. This line is called a secant. Any