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GEOMETRY. CHAPTER 1 1-1 Understanding points, lines and planes. Objectives. Students will be able to: Identify, name, and draw points, lines, segments, rays, and planes. Apply basic facts about points, lines, and planes . 1-1 Understanding lines .
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GEOMETRY CHAPTER 1 1-1 Understanding points, lines and planes
Objectives • Students will be able to: • Identify, name, and draw points, lines, segments, rays, • and planes. • Apply basic facts about points, lines, and planes.
1-1 Understanding lines • The most basic figures in geometry are undefined terms, which cannot be defined by using other figures. The undefined terms point, line, and plane are the building blocks of geometry.
K L M N Collinear Points • Points that lie on the same line are collinear. • Based on the definition. Which points are collinear? Which are not? K, L, and M are collinear. K, L, and N are noncollinear.
Coplanar points • Points that lie on the same plane are coplanar. Otherwisethey are noncoplanar. • Example of Coplanar • All the points A, B, C, and D in the plane P are coplanar.
Example 1 • Use the following figure to answer the following questions: • A) Name three collinear points Answer: D,E and F B) Name Coplanar points Answer: D,E,F and G C)Name a point that is noncollinear and a point that is not coplanar. • Answer: noncollinear is g and noncoplanar is h
Example 2 • Draw a line segment with endpoints a and b • A B • Draw ray with endpoint e and pass through d • D E • Draw line gh • g h
Postulates • A postulate, or axiom, is a statement that is accepted as true without proof. Postulates about points, lines, and planes help describe geometric properties.
Example 3 Name a line that passes through two points Answer: cd Name a plane that contains three noncollinear points. Answer; plane ABC
Intersecting lines • An intersection is the set of all points that two or more figures have in common. The next two postulates describe intersections involving lines and planes. Use a dashed line to show the hidden parts of any figure that you are drawing. A dashed line will indicate the part of the figure that is not seen.
Example 4 • Representing Intersections • A. Sketch two lines intersecting in exactly one point. B. Sketch a figure that shows a line that lies in a plane.
Homework • Page 9 13-21
Closure • Today we saw about point, lines, lines segments and rays and how we label them. We also saw collinear and coplanar points. Tomorrow we are going to continue with lesson 1-2.