The extraordinary shape

Circle

Why circle is extraordinary?Circle is much different shape from the

others because: It has no sides Has infinity axis of symmetry. Have other parameters then other figures.

Parameters of circle1. The middle of circle – We mark it with

letter „O” or „S”2. Diameter – We mark it with letter „D”. It

passes through the middle of the circle, it’s straight and her points are on the circle’s line.

3. Radius – It’s just the half of the diameter. We mark it with letter „R” and it goes from the middle of circle to the circle’s line.

Perimeter and Area of circleHow to count the perimeter of circle?

P = 2 πrO – perimeter

Pi number = 3,14r = radius of the circle

How to count the area of circle?

P = πr2

Checking taskCount the area of circle when the radius is

6 cm.We must use the definition here.

P = 3,14 x 62P = 3,14 x 36

P = 113,04 cm2The area of circle is 113,04 cm2

Task 2Count the perimeter of circle when the

radius is 9 cm. (In some cases you can use the

symbol  π instead of number 3,14) O = 2 πr

O = 18 πThe perimeter is 18  π cm.

Thank You for watching!

Jakub Samul