8.1 Points, Lines, Planes and Angles Flashcards
Undefined terms
Point, line, plane, and angle
Postulates (axiums)
Statements we accept as true because they are obvious
Theorems
Statements that are proven using deductive reasoning
Point
A location in space
Line
A set of points that extend forever in all directions
Ray
Part of a line that consists of one endpoint and extends forever in one direction
Line segment
A part of a line that consists of two endpoints and all the points in between
Plane
A flat, 2D surface that extends forever in all directions
Parallel lines
Two lines in the same plane that do not intersect (parallel planes are two planes that do not intersect)
Skew lines
Two lines that do not lie in the same place (noncoplanar) and do not intersect
Angle
The union of two rays with a common end point (when writing vertex–or common point– has to be in the middle)
Measure of an angle
Amount of rotation from its initial side to its terminal side
Symbol: m(angle symbol)
Measured in degrees
Right angle
90°
Acute angle
More than 0° less than 90°
Obtuse angle
More than 90° less than 180°
