- By
**emile** - Follow User

- 128 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' Investigating Circles' - emile

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

diameter

Circle

A closed curved

with all points

the same

distance from

center

•

origin

area

circumference

Origin

- The origin is the center of the circle.
- All points on a circle are the same distance from the origin.
- A circle is named by its center.
- Name: Circle A

origin

A

Diameter

- The diameter is the distance of a line segment going across a circle through its center. AB
- It divides the circle exactly in half.
- Is viewed as a line of symmetry.
- Symbol islower case d.

diameter

Radius

- Radius is the distance from the center of the circle to any point on the circle.
- Radius is one-half the length of the diameter.
- Symbol is lower case r.

Circumference

- Circumference refers to the total distance around the outside of a circle.
- Can also be called the perimeter of a circle.
- Symbol is an upper case C.

Making Connections

- You can estimate the age of a tree by measuring the circumference of a tree. For many kinds of trees, each 2 cm represents one year of growth.

100 cm

Making Connections

- An odometer is an instrument used to measure the distance a vehicle travels by counting the number of wheel revolutions.

Circle Properties

- closed curved
- all points same distance from centre (origin)
- radius
- diameter
- circumference
- area
- pi

Diameter

Radius

Circumference

Ratio of C & d

center of a circle

distance across center of circle (d)

half the distance of diameter (r)

distance around the outside of a circle ( C )

Circumference is actually 3.14 ( )

bigger than the diameter or about 3 times bigger

Concepts you Should Now KnowRatio Of The Circumference Of A Circle To Its Diameter

- If you measure the distance around a circle (C) and divide it by the distance across the circle through its center (d), you should always come close to a particular value
- We use the Greek letter to represent this value.

(pi)

Ratio Of The Circumference Of A Circle To Its Diameter

- The value of is approximately 3.14159265358979323. . .
- So, C/d always = ___
- Using is a quicker way to find the circumference of a circle.
- Using allow us to calculate circumference with less measuring,

(pi)

How Helps

2cm

- Knowing the value of ,allows us to use formulas to calculate circumference.
- If the diameter of a circle is 2 cm, how could you calculate the circumference?
- C = x ___
- Estimate the circumference
- The circumference is ____

Circumference of a Circle

Estimate

Is . . .

- C = x d
- C = 3.14 x 1.5
- C = 4.71cm

If the

diameter is 1.5cm

Circumference of a Circle

C = x d

…but we don’t know the diameter

- C = x d
- d = 2 x r
- d = 2 x 3
- d = 6
- C = 3.14 x 6
- C = 18.84m

If the

radius is 3m

Diameter of a Circle

What formula could I use?

What is the diameter of a circle if the

circumference

is 18.8?

Estimate the area of this circle.

Seeing the square units can help.

Remember each block is one square unit

Estimate is

Counting square units can give you a good estimate, however, can be time consuming.

Counting will not always give an exact answer.

Actual is

The formula for finding the area of a circle is

A = x r x r

or r2

Estimate is

Choosing a Formula

- To cut across a circular park has a you would travel 0.8 of a kilometer. How far would you travel around the park?
- A spoke of a bicycle wheel is 12 cm. What will be the distance of one turn of the wheel?

Multiplying Binomials

(2x – 6)(x + 7)

Other SkillsFactoring

2x² + 14x + 12

Find a. b. c.

Multiply a x c

Find two numbers

that add to b

( )( )

x in each

Divide by a

Kickback

Factoring

3x² + 12x + 12

Download Presentation

Connecting to Server..