1-4 Segments, Rays, Parallel Lines, and Planes
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Transcript of 1-4 Segments, Rays, Parallel Lines, and Planes
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1-4 Segments, Rays, Parallel Lines, and Planes
Objectives:
• Define line segments and rays
• Properly name line segments and rays
• Identify parallel lines and skew lines
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Line Segments
• A line segment is part of a line containing two endpoints and all points between them.
• Unlike lines, which extend forever in both directions, line segments have a definite beginning and end
• A line segment is named with the endpoints
A B
AB or BA
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Rays
• A ray is part of a line that consists of one endpoint and all points of the line extending in one direction
• Name a ray using the endpoint first and then another point on the ray– When naming, make sure the arrow points away from the
endpoint.
A
B
AB , not BA
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Rays, continued
• Are these two rays the same?
A
B
A
B
No• Different endpoints• Extend in different directions
BA
AB
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Opposite Rays
• Are two collinear rays with the same endpoint
• Always form a line
JK
L
KJ and KL are opposite rays
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Parallel Lines
• Lines that– Never intersect– Extend in the same directions– Coplanar
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Skew lines
Lines that:
• Never intersect
• Are noncoplanar
• Extend in different directions
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Parallel Planes
• Parallel planes are planes that never intersect– Example: the purple planes in the above
illustration
• A line and plane that never intersect are also parallel
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Learning Check and Summary• Which of the following has no endpoints?
– Ray, Line Segment, Line• Which of the following has two endpoints?
– Ray, Line Segment, Line• Which of the following has one endpoint and
extends in one direction?– Ray, Line Segment, Line
• Which of the following extend in the same direction?– Parallel lines, skew lines
• Which of the following extend in different directions?– Parallel lines, skew lines
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Exercises
• P. 13-15 All
• P. 253 All
• P. 255 All