circles circumference, diameter and radius. important info. you’ll need: notebook, pencil, and...

CirclesCircumference, Diameter and Radius

Important Info.You’ll need: notebook, pencil, and formula card.Pause. Rewind. Volume.Questions?

Area & PerimeterArea: CoveringPerimeter: SurroundingPolygons: Triangles, Rectangles, Squares, Parallelograms, Trapezoids

What is a circle?Not a polygon.

A plane figure with three or more straight sides and angles.

Definition: a closed plane figure made up of all the points the same distance from a point called the center.

E

Circle E

F

G

H

EF EGEH

==

radius

E

Circle E

F

EF

diameter

I+ EI= IF

½½

radius + radius = diameterr + r = d2r = d

Things You Should Know...

Radius (Plural: Radii)

A straight line from the center of a circle to it circumference.

It is half of the diameter.

Radius = r

Diameter

A straight line passing through the center of a circle connecting 2 points on the circumference.

It is twice the radius.

Diameter = d

CircumferenceDistance around a circle.C=2πr orC=πdπ = 22/7 ≈ 3.14

Finding CircumferenceC=2πr

Use this formula when you are given the radius.

C=πd

Use this formula when you are given the diameter.

Find the circumference of each circle. Use 3.14 for π.

4 cm

Find the circumference of each circle. Use 3.14 for π.

6 in

Find the circumference of each circle. Use 3.14 for π.

2.1 m

Find the circumference of each circle. Use 3.14 for π.

3.3 ft

http://bit.ly/12PtlS0How much do you know?

QuestionsEmail:

sgrey@spotswood.k12.nj.usllayton@spotswood.k12.nj.usmaussicker@spotswood.k12.nj.us

Before school tomorrow.Extra help on Mondays and Wednesdays.