# 9th Grade Honors Geometry MidTerms Study Guide

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Contains all definitions, properties, postulates, theorems, and corollaries in Units 1, 2, 3, 4, 5, and 6.

### Space

The set of all points.

### Collinear Points

Points all in one line.

### Coplanar Points

Points all in one plane.

### Intersection (of 2 Figures)

The set of points that are in both figures.

### Line Segment

A part of a line that is bounded by two endpoints, and contains every point on the line between its endpoints.

### Ray

A part of a line which is finite in one direction, but infinite in the other.

### Opposite Rays

Ray SR and ray ST are called ________ ____ if S is between R and T.

### Postulate

An assumption used as a basis for mathematical reasoning; axiom

### Ruler Postulate (Postulate 1)

1) The points on a line can be paired with the real numbers in such a way that any two points can have the coordinates 0 and 1. 2) Once a coordinate system has been chosen in this way, the distance between any two points equals the absolute value of the difference of their coordinates.

### Segment Addition Postulate (Postulate 2)

If B is between A and C, then AB + BC = AC.

### Congruent

In geometry, two objects that have the same size and shape are called _________.

### Midpoint

The ________ of a segment is the point that divides the segment into two congruent segments.

### Bisector

A ________ of a segment is a line, segment, ray, or plane that intersects the segment at its midpoint.

### Angle (∠)

An _____ is the figure formed by two rays that have the same endpoint.

### Acute Angle

An angle with a measure that is between 0 and 90.

### Right Angle

An angle with a measure that is equal to 90.

### Obtuse Angle

An angle with a measure that is between 90 and 180.

### Straight Anglw

An angle with a measure that is equal to 180.

### Protractor Postulate (Postulate 3)

On line AB in a given plane, choose any point O between A and B. Consider ray OA and ray OB and all the rays that can be drawn from O on one side of line AB. These rays can be paired with the reals numbers from 0 to 180 in such a way that: a) Ray OA is paired with 0, and ray OB with 180. b) If ray OP is paired with x, and ray OW with y, then m∠POQ = |x-y|.

Example: