# Geometry - Chapter 1

## 36 terms

### Acute Angle

Angle measuring less than 90 degrees

### Obtuse Angle

Angle measuring more than 90 degrees

### Right Angle

Angle measuring exactly 90 degrees

### collinear

lying on the same line

### coplanar

lying on the same plane

### point, line, plane

Building blocks of Geometry, undefined terms

### line segment

two points (the endpoints) all the points between them that are on the line containing them.

### congruent segment

segments that have the same measure

### midpoint

a point ON a line segment that is equally distant from both endpoints.

### ray

all points on a line that lie on one side of a point (the ray's endpoint).

### congruent angles

angles that have the same measure

### angle

formed by two rays that share an endpoint so long as they do not overlap

### angle bisector

a ray that shares the vertex of the angle and divides the angle into two congruent angles.

### degrees

the unit in which angles are measured

### Vertical Angles

formed by intersecting lines and do not share a common/adjacent side.

### Linear Pair of Angles

a pair of angles that share a side and their non-shared side form a straight line (they are supplementary)

### supplementary angles

two angles whose sum is 180 degrees

### complimentary angles

two angles whose sum is 90 degrees

a pair of angles with a common vertex and a common side, but no common interior points

### area

The number of nonoverlapping unit squares of a given size that will exactly cover the interior of a plane figure.

### base of triangle

Any side of a triangle.

### between

Given three points A, B, and C, B is between A and C if and only if all three of the points lie on the same line, and AB + BC = AC

### bisect

To divide into two congruent parts

### circumference

the distance around a circle

### collinear

points that lie on the same line.

### construction

A method of creating a figure that is considered to be mathematically precise. Figures may be constructed by using a compass and straightedge, geometry software, or paper folding.

### coordinate

A number used to identify the location of a point.

### coordinate plane

a plane that is divided into four regions by a horizontal line called the x-axis and a vertical line called the y-axis.

### coplanar

points that lie on the same plane

### degree

A unit used to measure distances around a circle. One degree equals 1/360 of a full circle.

### diameter

A line segment that passes through the center of a circle and has its endpoints on the circle. It describes how wide the circle is.

### distance

the absolute value of the difference of the coordinates of the points.

### endpoint

a point at the end of a segment or ray

### exterior of an angle

The set of all points outside an angle.

### height

A line segment extending from the vertex or apex of a figure to its base and forming a right angle with the base or plane that contains the base.

### hypotenuse

the side of a right triangle opposite the right angle