The Art of Circles

The Art of Circles

Circles

• Round Figure

• No sides, rather many points that are the same distance from the center to create the circumference

• The outer boundary is called a CIRCUMFERENCE

• The space occupied by a complete circle's interior is called its AREA

Parts of the Circle

The Radius is a line segment from the center to the circumference   $R\ =\ D\div2$  

The Diameter is a line segment from circumference to circumference passing through the center of the circle  $D\ =\ 2\times R$   

Fill in the Blanks

If the diameter measures 16cm, what is the radius?

Fill in the Blanks

If a radius is 13in, what is the diameter?

Multiple Choice

A circular carpet on the living room floor has a diameter of 64 inches. How can you find the radius of this carpet?

• Multiply the diameter by 2, the radius is 128 inches

• Divide the diameter by 2, the radius is 32 inches

• The radius and the diameter are the same

• Not enough information was provided

Multiple Choice

A clock has a radius of 21cm. How can you find the diameter of this clock?

• Not enough information is provided

• The diameter and radius are the same

• Multiply the radius by 2, the diameter is 42cm

• Divide the radius by 2, the diameter is 10.5cm

Circumference

The circumference is the perimeter of a circle

To find the measurement of circumference we can...

 $C=d\pi$    or    $C=2\pi r$  

Multiply the diameter by pie or multiply the radius by two then by pie

Pi

The number $\pi$  is a mathematical constant. It is defined as the ratio of a circle's circumference to its diameter. 

 $\pi$  is approximately 3.14  in numerical value. 

We could estimate  $\pi$  as 3

Multiple Choice

Use the image provided. What is the circumference of the circle?

• 31.4 cm

• 13.14 cm

• 15.7 cm

• 6.86 cm

Multiple Choice

Use the image provided. What is the circumference of the circle?

• 10.14 in

• 21.98 in

• 3.86 in

• 43.96 in