1.1.1 Understanding Points, Lines, and Planes

Question 1

undefined term

Answer 1

A basic geometric figure that cannot be defined in terms of other figures

Question 2

point

Answer 2

• it names a location and has no size. It is represented by a dot
• The dot must have some thickness or size when drawn, but an idealized point has no size because it is only a location
• A point is named with a capital letter, such as P.

Question 3

line

Answer 3

• it is a straight path that has no thickness and extends forever
• An idealized line contains an infinite number of points and has length, but no thickness.
• A line is named with a lowercase letter or by drawing a double-headed arrow over the names of two points on that line

Question 4

plane

Answer 4

• it is a flat surface that has no thickness and extends forever
• Points and lines are contained on a plane. A plane is named with a capital script letter, such as R , or with any three points on that plane, and these points are not on a single line.

Question 5

collinear

Answer 5

Points that lie on the same line

Question 6

coplanar

Answer 6

Points that lie in the same plane

Question 7

segment or line segment

Answer 7

• it is the part of a line consisting of two points and all points between them
• A segment is named by drawing a line (with no arrows) over the names of the two endpoints

Question 8

endpoint

Answer 8

it is a point at the end of a segment or the starting point of a ray

Question 9

ray

Answer 9

• it is a part of a line that starts at an endpoint and extends forever in one direction
• A ray is named by drawing a single-headed arrow over the name of the endpoint and any other point on that ray

Question 10

opposite rays

Answer 10

• they are two rays that have a common endpoint and form a line

Question 11

postulate or axiom

Answer 11

it is a statement that is accepted as true without proof

Question 12

intersection

Answer 12

it is the set of all points that two or more figures have in common

Question 13

postulate

Answer 13

• Through any two points there is exactly one line.
• Through any three noncollinear points there is exactly one plane.
• If two points lie in a plane, then the line containing those points lies in the plane.
• If two unique lines intersect, then they intersect at exactly one point.
• If two unique planes intersect, then they intersect at exactly one line.

Question 14

geometry

Answer 14

it is an area of mathematics concerned with the study of two-dimensional and three-dimensional figures. Before a
figure can be studied in geometry, even the most basic parts of the figure must be identified and named. For example, consider
a triangle. A triangle is a very simple figure with three sides where each pair of sides meets at a corner. Even though a triangle
is a simple figure, its parts must be identified using geometric terms before a triangle can be explicitly defined