# Geometry

## 34 terms

coplanar angle that have a common vertex and one common side, but no common interior points - next to each other!

### Vertical Angles

two non-adjacent angles formed by two intersecting lines - across from each other!

### Linear Angles

two adjacent angles whose non-common sides are two rays going in opposite directions - two angles that make a line!

### Complementary Angles

Sum of the measures of the two angles is 90 degrees.

### Supplementary Angles

Sum of the measures of the two angles is 180 degrees. If two angles form a linear pair, they are supplementary.

### Collinear

A set of point all lined on the same line.

### Coplanar

A set of points or lines all lying on the same plane.

### Skew

Non-Coplanar lines that never intersect.

### Parallels

Coplanar lines that never intersect.

### Perpendicular Lines

Lines that intersect to form right angles.

### Line Segment

A portion of a line with two end points.

### Ray

Portion of a line with one end point.

### Segment Bisector

A segment, line or ray that divides a segment into two congruent halves.

### Angle Bisector

A line or ray that divides an angle in half.

### Y-Intercept

the point where a graph intersects the y-axis.

### Slope

the steepness of a line; constant rate of change;change in y over change in x.

### Conditional Statement

an "If, then" statement' the part after "if" is the hypothesis and the part after "then" is the conclusion.

### Converse

switching the hypothesis and conclusion of a conditional statement.

### Inverse

negating the hypothesis and conclusion of a conditional statement.

### Contrapositive

Switching and negating the hypothesis and conclusion of a conditional statement.

### Point

an undefined term; has no length, with, or thickness(no dimensions); and represents a location in space.

### Line

an undefined term; has no width or thickness (one dimension - length); continues forever in two directions.

### Plane

an undefined term; has no thickness (two dimensions - length & width); continues forever in all directions; a flat surface.

### Theorem

a statement that is proven.

### Postulate

a statement that is accepted as true without proof.

### counter-example

something that proves a statement false.

### Linear Pair

two adjacent angles whose non-common sides are two rays going in opposite directions-two angles that make a line.

### center of dilation

In a dilation, the fixed point about which the figure is enlarged or reduced. It's also the intersection point of the lines that extend through the corresponding vertices of the original and dilated image.

### pre-image

the figure before the transformation is applied.

### image

the figure after the transformation is applied, indicated by primes - A'B'C'

### scale factor

the ratio used to enlarge or reduce similar figures.

### congruent figures

figures that are the same size and same shape - angles and side lengths are all congruent.

### similar figures

figures that are the same shape but different size - angles are congruent and sides are proportional.

### isometric transformations

transformations in which the pre-image and image are congruent figures: rotations, translations, reflections.