Vocabulary #1.1 (Tools of Geometry)

Polygon

A closed figure with straight sides. The intersection of two sides in a polygon is called a vertex.

Line

A line is a set of points extending without end in opposite directions. Lines can be curved or straight, are one dimensional and have an infinite length but have no height or thickness. They are represented by a double arrow to indicate its infinite length.

Angle bisector

A line, segment, or ray passing through the vertex of a triangle and bisecting that angle.

Plane

A plane is a set of points that form a flat surface.They are two dimensional and have an infinite length and width but no height.

Point

A point is a location in space. It is zero dimensional, having no length, width, or thickness. Points are infinitely small.

Ray

A portion of a line that has one endpoint and continues infinitely in one direction. When two rays share an endpoint and form a straight line, the rays are called opposite rays.

Line segment

A portion of a line with two endpoints. The length of a segment is the distance between the two endpoints. To specify a particular starting point and ending point for a segment, you use a direct segment.

Altitude

A segment from a vertex perpendicular to the opposite side.

Median

A segment from a vertex to the midpoint of the other side.

Perpendicular bisector

A segment, line, or ray that is perpendicular to and passes through the midpoint of a side.

Acute- ... Right- ... Obtuse- ...

A- all angles are acute R- one right angle O- one obtuse angle

Acute angle- ___ Right angle- ___ Obtuse angle- ___ Straight angle- ___

Aa- an angle whose measure is less than 90 deg Ra- exactly 90 deg Oa- more than 90 deg but less than 180 deg Sa- exactly 180 deg

Adjacent angles

Angles that share a common ray and vertex but no interior points.

Four special segments can be drawn in a triangle, and every triangle has three of each.

They are altitude, median, angle bisector, and perpendicular bisector.

What is a regular?

When all sides of a polygon are congruent to one another (equilateral) and all the angles are congruent (equiangular). A square is an ex. of a regular quadrilateral.

Angle

Is a union of two rays with a common endpoint, which is called the vertex. The measure of an angle can be specified by using the letter m. Ex. m<RST=30 degrees

Scalene- ___ Isosceles- ___ Equilateral- ___

S- no congruent sides or angles I- at least two congruent sides, two congruent angles E- three congruent sides and angles

How many sides? Triangle, Hexagon, Quadrilateral, Octagon, Pentagon, and Decagon

T- 3, H- 6, Q- 4, O- 8, P- 5, D- 10

*Remember...

that an infinite number of points are on any line, ray, or segment and that lines, rays, and segments can be considered to exist.