Unit 1: Postulates & Theorems Flashcards
Ruler Postulate
A shared understanding of how to use a ruler properly:
1. choose a consistent scale with equal increments
2. calculate the length (measure) by absolute distance
Segment Addition Postulate
If B is between A and C, then AB + BC = AC
Protractor Postulate
On line AB in a given plane, choose its midpoint (point O); all rays that can be drawn from O (ex: ray OA) are degrees
1. ray OA is 0 degrees, OB is 180
2. always measure the absolute value
Angle Addition Postulate
- If point B lies on the interior of <AOC, then m<AOB + m<BOC =mAOC
- If <AOC is a straight angle and B is any point not on AC, then m<AOC + m<BOC is 180 degrees
Line-Point Postulate
A line is defined by 2 or more points
Plane-Point Postulate
A plane has 3 or more points not all in 1 line
Space-Point Postulate
Space has 4 or more points not all in 1 plane of existence
Two-Point Postulate
Through any 2 points, there is exactly 1 line
Three-Point Postulate
Through any 3 points, there is at least 1 plane; any 3 noncollinear points there is exactly 1 plane
Plane-Line Postulate
If 2 points are on a plane, then the line containing said points is also on said plane
Plane Intersection Postulate
If 2 planes intersect, their intersection is a line
Line Intersection Theorem
If 2 lines intersect, then they intersect at exactly 1 point
Theorem: A Line and a Point Define a Plane
Through a line and a point not in the line, there is exactly 1 plane
Theorem: Two Lines Define a Plane
If 2 lines intersect, there is exactly 1 plane that contains the lines