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Geometry: Section 1.1 Name: Objective: To define and name points, lines, rays, segments, angles and triangles. Points: A point represents location. It has no size and is always named by a capital letter. Line: By line we mean a straight line composed of infinitely many points extending infinitely far in opposite directions. Naming a line: 1) Use a small cursive letter near the line. ˆm 2) Use any two points on a line, with line symbol above them. B C D Using this method, there are 6 ways to name this !line. ##" Finish them below. CB , , , , A line may be marked consistently with tick marks and numbers and become a number line. Line segments: A line segment or segment is a part of a line with two definite endpoints. It is named by its endpoints, with a segment symbol above the two endpoints. They are subsets of lines. Name these segments. A E D C F G B Rays: A subset or part of a line which has one endpoint and goes forever in one direction. They are always named by the endpoint first and then any other point on the ray with a ray symbol above the two letters. A C E F B D Angle: the union of two rays with a common endpoint. The common endpoint is called the vertex and the rays form the sides of the angle. Way to name angles: 1) An angle can be named by a number written inside the angle (with no degree sign) A 2 B !2 C 2) An angle can be named by its vertex A C B !B 3) An angle can be named by three points on the angle, but the vertex must be the middle point. H A 2 1 B ! ABC Name ! 1 and ! 2. ! 1 can be named C ! 2 can be named Why must three letters be used to name these angles? Triangle: The union of three segments with common endpoints. The endpoints are called the vertices of the triangle. The segments are the sides of the triangle. We name a triangle by its three vertices. ∆ABC or ∆ACB or ∆CAB, etc. A B ! ABC = AB ! BC ! AC C Homework: 1.1, pg. 7-8, # 1, 3, 5-14 all