# Understanding Points Lines and Planes 1 1 Lines

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Understanding Points, Lines, and Planes 1 -1 Lines, and Planes Warm Up Lesson Presentation Lesson Quiz Geometry Holt. Mc. Dougal. Geometry Holt

1 -1 Understanding Points, Lines, and Planes Objectives Identify, name, and draw points, lines, segments, rays, and planes. Apply basic facts about points, lines, and planes. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Vocabulary undefined term line collinear segment ray postulate Holt Mc. Dougal Geometry point plane coplanar endpoint opposite rays

1 -1 Understanding Points, Lines, and Planes 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. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Points that lie on the same line are collinear. K, L, and M are collinear. K, L, and N are noncollinear. Points that lie on the same plane are coplanar. Otherwise they are noncoplanar. K L M N Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Example 1: Naming Points, Lines, and Planes A. Name four coplanar points. A, B, C, D B. Name three lines. Possible answer: AE, BE, CE Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Check It Out! Example 1 Use the diagram to name two planes. Possible answer: Plane R and plane ABC. Holt Mc. Dougal Geometry

. Understanding Points, Lines, and Planes 1 -1 EXAMPLE Name points, 1 lines, and planes a. Give two other names for PQ and for plane R. Name three points that are collinear. Name four points that are coplanar. SOLUTION Other names for PQ are QP and line n. Other names for plane R are plane SVT and plane PTV. Holt Mc. Dougal Geometry

Understanding Points, Lines, and Planes 1 -1 EXAMPLE Name points, 1 lines, and planes b. Points S, P, and T lie on the same line, so they are collinear. c. Points S, P, T, and V lie in the same plane, so they are coplanar. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes GUIDED PRACTICE for Example 1 1. Use the diagram in Example 1. Give two other names for ST. Name a point that is not coplanar with points Q, S, and T. ANSWER Holt Mc. Dougal Geometry TS, PT; point V

1 -1 Understanding Points, Lines, and Planes Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Example 2: Drawing Segments and Rays Draw and label each of the following. A. a segment with endpoints M and N. N M B. opposite rays with a common endpoint T. T Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Check It Out! Example 2 Draw and label a ray with endpoint M that contains N. M Holt Mc. Dougal Geometry N

1 -1 Understanding Points, Lines, and Planes Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Example 3: Identifying Points and Lines in a Plane Name a line that passes through two points. XY Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Check It Out! Example 3 Name a plane that contains three noncollinear points. Possible answer: plane GHF Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Holt Mc. Dougal Geometry

1 -1 Understanding Points, 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. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes 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. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Check It Out! Example 4 Sketch a figure that shows two lines intersect in one point in a plane, but only one of the lines lies in the plane. Holt Mc. Dougal Geometry

Understanding Points, Lines, and Planes 1 -1 EXAMPLE Sketch 3 intersections of lines and planes Sketch a plane and a line that is in the plane. b. Sketch a plane and a line that does not intersect the plane. c. Sketch a plane and a line that intersects the plane at a point. SOLUTION c. a. b. Holt Mc. Dougal Geometry

Understanding Points, Lines, and Planes 1 -1 EXAMPLE Sketch intersections of planes 4 Sketch two planes that intersect in a line. SOLUTION P 1 Draw: a vertical plane. Shade the plane. STEP 2 Draw: a second plane that is horizontal. Shade this plane a different color. Use dashed lines to show where one plane is hidden. STEP 3 Draw: the line of intersection. Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes GUIDED PRACTICE for Examples 3 and 4 4. Sketch two different lines that intersect a plane at the same point. ANSWER Use the diagram at the right. 5. Name the intersection of PQ and line k. ANSWER Holt Mc. Dougal Geometry Point M

1 -1 Understanding Points, Lines, and Planes Lesson Quiz: Part I 1. Two opposite rays. CB and CD 2. A point on BC. Possible answer: D 3. The intersection of plane N and plane T. Possible answer: BD 4. A plane containing E, D, and B. Plane T Holt Mc. Dougal Geometry

1 -1 Understanding Points, Lines, and Planes Lesson Quiz: Part II Draw each of the following. 5. a line intersecting a plane at one point 6. a ray with endpoint P that passes through Q Holt Mc. Dougal Geometry