## 66 terms

### Transformation

The mapping, or movement, of all the points of a figure in a plane according to a common operation.

### Reflection

A transformation that "flips" a figure over a mirror or reflection line.

### Reflection Line

A line that acts as a mirror in the form of a perpendicular bisector so that corresponding points are the same distance from the mirror.

### Translation

A transformation that "slides" each point of a figure the same distance in the same direction.

### Rotation

A transformation that turns a figure about a fixed point at a given angle and a given direction.

### Angle Bisector

A segment or ray that shares a common endpoint with an angle and divides the angle into two equal parts.

### Bisector of a Line

In a plane, divides a line segment into two congruent segments.

### Parallel Lines

Two lines that lie in the same plane and they do not intersect.

### Perpendicular lines

Two lines that intersect to form a right angle.

### Congruent

Having the same size and the same shape.

### Congruent figures

Figures that have the same size and the same shape.

### Point

A dot that has no length, width, or thickness. It is identified by a capital letter.

### Line

Has no thickness but its length goes on forever in two directions.

### Plane

Goes on forever in all directions (in two-dimensions) and is "flat" (i.e., it has no thickness).

### Line segment

The part of a line between two points on the line. Sometimes referred to as a segment.

### Endpoint

The point at an end of a line segment.

### Point of Intersection

The point at which two or more lines intersect (cross).

### Ray

A ray begins at a point and goes on forever in one direction.

### Corresponding sides

Sides that have the same relative positions in geometric figures.

### Corresponding angles

Angles that have the same relative positions in geometric figures.

### Angle

Region between two rays or the amount of rotation about a fixed point.

### Angle of rotation

The number of degrees that a figure is rotated about a fixed point.

### Dilation

A transformation that changes the size of an object, but not the shape.

### Proportion

An equation which states that two ratios are equal.

### Ratio

A comparison of two quantities that have the same unit of measure.

### Scale Factor

The ratio of corresponding lengths of the sides of two similar figures.

### Similar Figure

Figures that have the same shape but not necessarily the same size.

### Cone

A three dimensional figure with a circular or elliptical base and one vertex.

### Base of a cone

Can be a circle or an ellipse.

### Oblique cone

A cone whose axis is not perpendicular to it's base. It is tilted.

### Right circular cone

A three-dimensional figure that is generated by rotating a
right triangle about one of its legs.

### Cross section

A plane figure obtained by slicing a solid with a plane.

### Cube

A regular polyhedron whose six faces are congruent squares.

### Cylinder

A three-dimensional object with two parallel congruent circular bases.

### Base of a Cylinder

The two congruent and parallel circular regions that form the ends of the cylinder. (circles)

### Oblique Cylinder

A cylinder with bases that are not aligned one directly above the other. It is tilted.

### Right Circular Cylinder

A cylinder with circular bases that are aligned one directly above the other.

### Polyhedron

A collection of polygons joined at their edges. Each of these polygons is called a "face."

### Prism

A polyhedron with two parallel and congruent faces and all other faces that are parallelograms.

### Bases of a prism

The two faces formed by congruent polygons that lie in parallel planes, all of the other faces being parallelograms.

### Lateral faces of a prism

A face that is not the base of the solid.

### Rectangular prism

A prism whose bases are rectangles.

### Right rectangular prism

A prism whose faces and bases are rectangles.

### Pyramid

A pyramid is a polyhedron with one face (the "base") a polygon and all the other faces triangles meeting at a common point called the vertex.

### Base of a Pyramid.

The face that does not intersect the other faces at the vertex. The base is a polygonal region. It's base is usually a square or rectangle.

### Lateral faces of a pyramid

Faces that intersect at the vertex.

### Right pyramid

A pyramid that has its vertex aligned directly above the center of its base.

### Acute Angle

An acute angle is an angle whose measure is between 0 degrees and 89 degrees. Smaller than 90 degrees.

### Acute triangle

A triangle with three acute angles.

Angles in the same plane that have a common vertex and a common side, but no common interior points.

### ASA (Angle Side Angle)

Theorem- two triangles are congruent if.... two angles and their included side of one triangle are congruent to the corresponding sides and angles of the second triangle.

### Center of Rotation

The point in which a figure is rotated

### Complementary angle

Two angles whose sums measures 90 degrees.

### Equilateral triangle

A triangle with three equal sides.

### Line Symmetry

If a figure has one half a mirror image of the other half.

### Obtuse angle

An angle that measures more than 90 degrees.

### Right angle

An angle that measures 90 degrees.

### Isosceles Triangle

A triangle with at least two sides having equal lengths.

### Right Triangle

a triangle with a 90 degree (right) angle

### SAS (Side Angle Side)

Theorem- two triangles are congruent if.... two sides and their included angle of one triangle are congruent to the corresponding sides and angles of the second triangle.

### Scalene Triangle

A triangle with no equal sides.

### Skew Lines

Two lines that do not lie in the same plane (therefore, they cannot be parallel or intersect).

### Straight angle

A straight angle is formed by a straight line and measures exactly 180 degrees.

### Transversal

A line that crosses two or more lines.

### Vertex

On a angle or a polygon the point where two sides intersect

### Vertical angles

A pair of opposite, congruent angles formed by intersecting lines.