A plane is a flat surface that goes on and on in all directions.

A plane figure is a flat geometric shape.

A polygon is a closed plane figure made up of three or more line segments (sides) that are connected.

A vertex is the point where two sides of a polygon meet. The plural of vertex is vertices.

vertices

Polygons are named by the number of sides they have.

A triangle has 3 sides.

A quadrilateral has 4 sides.

A pentagon has 5 sides.

A hexagon has 6 sides.

An octagon has 8 sides.

There are also names for polygons with seven sides, nine sides, and any number of sides!

The perimeter of a figure is the distance around the outside.

What is the perimeter of each of these polygons?

12 in.

12 in.

6 in. 6 in.P = 36 in.

8 units

11 units

9 units9 units

18 ft.

16 ft. 16 ft.

10 m.

5 m. 4 m.

5 m.

15 m.

P = 37 units

P = 50 ft.

P = 39 m.

The area of a flat surface is the number of square units needed to cover the surface.

What is the area of each of these polygons?

Count the square units to find out.

A = 20 sq. units

A = 104 sq. units

The area of a flat surface is the number of square units needed to cover the surface.

What is the area of each of these rectangles?

Multiply to find out.

A = 104 sq. units8 x 13 =

4 units

4 u

nit

s

A = 4 x 4 = 16 sq. units

A circle is a closed curve that is made of points that are the same distance from the center.

A line segment is a part of a line.

A radius is any line segment that connects the center to a point on the circle. A diameter is any line segment that passes through the center of a circle, connecting two points on the circle.

A diameter is twice as long as a radius.

The circumference is the distance around a circle.

The circumference of a circle is about 3 times the diameter.

C = about 3 x d

The area of a circle is the number of square units needed to cover the inside of the circle.

Find the approximate area of a circle by counting the square units inside or by multiplying the radius times the radius times 3.

A = about 3 x r x r

Find the approximate perimeters of the circles below.

R = 3 units R = 6 units

P = about ______ units.

A = about ______ sq. units. P = about ______ units.

A = about ______ sq. units.

18

3627

108

Congruent figures have the same size and shape.

Similar figures have the same shape. If they also have the same size, they are congruent.

A slide (translation) moves a figure up, down, or over.

A turn (rotation) rotates a plane figure.

A flip (reflection) is a mirror image of a figure.

A plane figure has symmetry if its halves match.

If a plane figure has symmetry, it can be folded so its halves match. The fold is called a line of symmetry.

How many lines of symmetry do each of these plane figures have?

A tessellation completely covers the inside space of a plane figure, usually in some kind of organized pattern.

Now use the tiles to experiment. Which tiles will tessellate a piece of math paper? Try squares, triangles, hexagons, etc. Will circles tessellate a plane figure? Explain your answer.

A three-dimensional object is called a space figure or a solid.

cuberectangular prism

cylinder

conepyramid sphere

cuberectangular prism

cylinder cone sphere

pyramid

FACE

cuberectangular prism

cylinder cone sphere

pyramid

VERTEX

cuberectangular prism

cylinder cone sphere

pyramid

EDGE

The number of cubic units inside a solid is called the volume.

= one cubic unit

V = ______ cubic units 6

The number of cubic units inside a solid is called the volume.

= one cubic unit

V = ______ cubic units24

Count the cubic units to find the volume of this figure.

V = ______ cubic units 22

V = ______ cubic units 36

TERM EXAMPLE SAYA point is an exact location in space.

A point A

A line is a collection of points that go on and on in both directions. It has no endpoints.

C

line BC

A line segment is part of a line. It has two endpoints.

line segment DE

A ray is part of a line. It has one endpoint and continues on and on in one direction.

F

G

ray FG

Intersecting lines are lines that pass through the same point.

line HK intersects line JI at point L

Parallel lines are lines that never intersect.

line JK is parallel to line BC.

BBB

D E

H I

J

J

KK

L

J K

B C

Two intersecting lines that form four right angles are perpendicular to each other.

A

B C

D

Line BC is perpendicular to line AD.

Two rays meet at a vertex, forming an angle.

An angle that forms a square corner is a right angle.

An angle greater than a right angle is an obtuse angle.

An angle less than a right angle is an acute angle.