1. 1.1 Identify Points, Lines, and Planes
Objective: Name and sketch geometric figures.
CA Standards: 1
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2. Vocabulary
In geometry, the terms point, line, and plane are
accepted as intuitive ideas and are not defined. These
undefined terms are then used in the definitions of
other terms.
A point A
A point can be represented by a dot,
but it does not have any size or
mass.
A line is made of points and extents j
in two directions. S T
line j ST TS
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3. Vocabulary
A plane is a flat surface that extends A Plane P
without ending and has no B
P c
thickness. Plane ABC
Collinear Points are all points in
one line.
A
Coplanar Points are points all in one B
plane. P c
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4. Vocabulary
Defined Terms that can be described using known
Terms words.
Line segment or segment AB
consists of the endpoint A and B. A B
AB BA
The ray AB consists of the Initial
Point A and all the points that lie A B
on the same side of A as point B. AB
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5. Vocabulary
Opposite Rays If C is between A and B,
A C B then CA and CB are opposites rays.
Intersection The intersection of two figures is the set
of points that are in both figures.
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6. Undefined Terms
Point A point has no dimension. It is
represented by a dot.
Line A line has one dimension. It is
represented by a line with two
arrowheads, but extends without end.
Through any two points, there is exactly
one line. You can use any two points
on a line to name it.
Plane A plane has two dimensions. It is represented by
a shape that looks like a floor or wall, but it extends
without end.
Through any three points not on the same line, there is
exactly one plane. You can use three points that are
not all on the same line to name a plane.
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7. Example 1
Give two other names for LN.
Given another name for plane Z.
Other names for LN are LM and line b.
Other names for plane Z are plane LMP and LNP.
Name three points that are collinear.
Name four points that are
coplanar.
Points L, M, and N lie on the same line, so
they are collinear. Points L, M, N, and P
lie on the same plane, so they are
coplanar.
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8. Give two other names for VX.
1. X, Y
2. WX, XW
3. WX, XW
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9. Defined Terms
Line AB (written as AB) and points A and B
are used here to define the terms below.
Segment The line segment AB, or segment AB,
(written as AB) consists of the endpoints A and B
and all points on AB that between A and B.
Note that AB can also be named BA
Ray The ray AB, (written as AB) consists of the endpoint A
and all points on AB that lie on the same side of A as B.
Note that AB and BA are different.
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10. Example 2
Give two other names for VX.
Another name for VX is XV.
Name all rays with endpoints W.
Which of these rays are opposite rays?
The rays with endpoint W are WV, WY, WX, and WX.
The opposite rays with endpoint W are WV and WX, WY, and WZ.
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11. Example 3
Sketch a plane and a Sketch a plane and a
line that intersects the line that is in the
plane at more than plane. Sketch another
one point. line that intersects the
line and plane at a
point.
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12. Example 4
Draw two planes that intersect in a line.
Step 1
Draw one plane as if you
are facing it.
Step 2
Draw a second plane that
is horizontal.
Use dashed lines to show
where one plane is hidden.
Step 3
Draw the line of intersection.
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13. Name the intersection of MX and line a.
1. X, Y
33% 33% 33%
2. c
3. M
1 2 3
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