# Geometry

Free Math Games & Activities for Kids

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 OperationsAddition Property of Equality:** 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 OperationsAddition Property of Inequality:** 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 OperationCommutative Property of Addition:** a
+ b = b + a

**Commutative Property of Multiplication:**a * b = b * a

**Distributive Property:**a * (b + c) = a * b + a * c and vice versa

Perimeter and Area

Geometry games (Shodor Interactive)

Shape Games

Planarity

Angles

Coordinates

Triangles

Squares

Polygons