2. What is the circle?
• The set of all points those are equidistant
from a fixed point is called a circle.
• The fixed is called center of the circle.
• The line segment between two points on the
circle which is passing through the center is
called the diameter.
• The line segment between any point on the
circle and the center is called the radius (plural
radii).
6. Finding the circumference
• The circumference of a circle is given by the
formula C = πD, where C is the circumference
and D is the diameter of a circle.
• Notice that D = 2xRadius = 2r
• π : an irrational number which is
approximately equal to 3.14.
9. Find the perimeter of each of the shapes below. (Remember to add the lengths of
the straight sections.)
10. A scooter tire has a diameter of 32 cm. What is the perimeter of the tire?
Find the circumference of the Ferris wheel shown below.
11.
12. Area of a circle
If the circle is divided into smaller
sectors, the curved sides of the
sectors become straighter and,
hence, the shape is closer to a
perfect rectangle.
13. Finding the area of a circle
• The area of a circle, A, can be found using the
formula A = π r2 , where π is a constant with a
value of approximately 3.14 and r is the radius
of the circle.