### Angle & Coordinate Plane – Geometry Basics

This chapter is about basics of Geometry including coordinate plane, angle, quadrant & congruent etc.

**Ordered Pair**

Points on the coordinate plane (x,y)

**X-Coordinate**

The first number in an ordered pair that correspongs to a number on the x-axis

**Y-Coordinate**

The second number in an ordered pair that corresponds to a number on the y-axis

**Quadrant**

The four regions of the coordinate plane created by the x-axis and y-axis

**Origin**

The point at which the axes intersect.

**Congruent**

Geometric figures that have exactly the same shape and size.

**Midpoint**

The point halfway between the endpoints of the segment.

**Segment Bisector**

Any segment, line or plane that intersects a segment at it’s midpoint.

**Angle**

Formed by two non-collinear rays that have a common endpoint

**Vertex**

The common endpoint of an angle

**Angle Bisector**

A ray that divides an angle into two congruent angles

**Point**

A location – it has neither shape nor size

**Line**

Made up of points and has no thickness or width.

**Plane**

A flat surface made up of points that extends infinitely in all directions

**Collinear**

Points that lie on the same line.

**Coplanar**

Points that lie in the same plane

**Intersection**

The set of points two or more geometric figures have in common.

**Space**

A Boundless 3-D set of all points

**Parallel**

Lines, segments, rays or planes that never intersect

**Perpendicular**

Lines, segments,rays or planes that form right angles.

**Parallel**

LinesCoplanar lines that do not intersect. Their slopes are equal.

**Transversal**

A line that intersects two or more lines in a plane at different

**pointsInterior**

AnglesAngles that lie between two transversal that intersect the same line

**Exterior Angles**

An angle formed by one side of triangle and the extension of another side

**Alternate Interior Angles**

Angles that are on opposite sides of the transversal and are in between the parallel lines

**Corresponding Angles**

Angles that are in the same position, but a different group of angles

**Alternate Exterior Angles**

Angles that are on opposite sides of the transversal and are outside the parallel lines

**Congruent segments**

line segments whose lengths are equal

**Horizontal Reflectional (Line) Symmetry**

reflectional symmetry about a horizontal line of reflection

**Midpoint of a Line Segment**

the point halfway between the endpoints of a line segment

**Perpendicular Lines**

lines in the same plane that intersect at 90 angles whose slopes are opposite reciprocals,

**Reflection**

**Transformation**

**Translation**

**Two-Dimensional Coordinate System**

two axes at right angles to each other, forming a xy-plane, consisting of points (x, y)

**Perpendicular Bisector**

a perpendicular segment that bisects a segment

**Concurrent LInes**

when three or more lines intersect at a common point

**Point of Concurrency**

the point where concurrent lines intersect

**Circumcenter**

the point where perpendicular bisectors of a triangle are concurrent

**Incenter**

the point where angle bisectors of a triangle are concurrent

**Median**

a segment that connects a vertex of a triangle with the midpoint of the opposite side

**Centroid**

the point where the medians of a triangle are concurrent

**Altitude**

**Orthocenter **

the point where the altitudes of a triangle are concurrent

**point**

a location

**line**

made up of points and has no thickness or width

**plane**

a flat surface that extends forever in all directions

**Noncollinear**

points that do not lie on the same line

**Collinear**

points that lie on the same line

**Noncoplanar**

points that do not lie on the same plane

**Coplanar**

points that lie on the same plane

**congruent**

Having the same measure

**line segment**

part of a line with two endpoints

**angle**

amount of rotation between two lines (or rays) around a common point (vertex)

**angle bistector**

ray or line that divides an angle into two congruent angles

**adjacent angles**

Two angles next to each other that share a common side and have the same vertex

**supplementary angles**

two angles that add up to 180 degrees

**complementary angles**

two angles that add up to 90 degrees

**vertical angles**

the angles opposite each other when two lines cross

**perpendicular lines**

Two lines that intersect to form right angles (90 degrees)

**distance**

the length between two points

**midpoint**

A point that divides a segment into two congruent segments

**concave**

polygon with a “dent” or “caved in”

**convex**

polygon with no “dents”

**regular polygon**

a polygon that is both equilateral and equiangular

**equilateral triangle**

A triangle with 3 congruent sides and 3 congruent angles.

**Equiangular**

all angles are congruent

**isosceles triangle**

a triangle with two congruent sides and two congruent angles

**scalene triangle**

a triangle with no congruent sides

**consecutive interior angles**

two angles that lie between the two lines and on the same side of the transversal

**alternate interior angles**

Interior angles that lie on opposite sides of the transversal

**alternate exterior angles**

Angles that lie outside a pair of lines and on opposite sides of a transversal.

**corresponding angles**

lie on the same side of the transversal and in corresponding positions

**vertex angle**

The angle formed by the legs of an isosceles triangle.