Geometry is a branch of mathematics concerned with the relations of points, lines, surfaces, solids and shapes.

A point is an exact location in space. They are shown as dots on a plane in two dimensions or a dot in space in three dimensions. A point is labeled with capital letters.

A line is a geometric figure that consists of an infinite number of points lined up straight that extend in both directions, forever, indicated by the arrows at the end.

A line segment is a part of a line with two endpoints. A line segment starts and stops at the two endpoints.

A ray is part of a line with one endpoint and extends in one direction forever.

A plane is a flat two dimensional surface. A plane can be identified by three points in the plane or by a capital letter. There is exactly one plane through three points. The intersection of two planes is a line.

An angle consists of two rays with a common endpoint. The two rays is called the side of the angle and the common endpoint is the vertex of the angle. Each angle has a measurement generated by the rotation about the vertex. The measure is determined by the rotation of the terminal side about the initial side. Angles can be classified based upon the measure.

Rules in Algebra and Geometry:

Postulates of Equality
Reflexive Property of Equality: a = a
Symmetric Property of Equality: if a = b, then b = a
Transitive Property of Equality: if a = b and b = c, then a = c

Postulates of Equality and Operations
if a = b, then a + c = b + c
Multiplication Property of Equality: if a = b, then a * c = b * c
Substitution Property of Equality: if a = b, then a can be substituted for b in any equation or inequality
Subtraction Property of Equality: if a = b, then a - c = b - c

Postulates of Inequality and Operations
if a < > b, then a + c < > b + c
Multiplication Property of Inequality: if a < b and c > 0, then a * c < b * c
if a < b and c < 0, then a * c > b * c
Equation to Inequality Property: if a and b are positive, and a + b = c, then c > a and c > b
if a and b are negative, and a + b = c, then c < a and c < b
Subtraction Property of Inequality: if a < > b, then a - c < > b - c
Transitive Property of Inequality: if a < b and b < c, then a < c

Postulates of Operation
a + b = b + a
Commutative Property of Multiplication: a * b = b * a
Distributive Property: a * (b + c) = a * b + a * c and vice versa

Geometry Games:

Perimeter and Area Geometry Games

Math Games - Geometry

Visual Geometry Games

Geometry games (Shodor Interactive)

Shape Games Geometry

Planarity Geometry Game

Geometry PK-2

Tessellations

Transformations

Angles Geometry Game

Coordinates Geometry Game

Solid Geometry - 3D Shapes

Maze Games

k12 flash Geometry Games

Pattern Blocks

Triangles Geometry Game

Squares Geometry Game

Rectangles

Circles

Polygons Geometry Game

Congruent & Similar Shapes

Dr. Math

Geometry Jeopardy

Math Games

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