Circle

Basic Term of Circle

• Circle: closed curve in a plane where every point on the curve is equidistant from a fixed point.
• Centre: fixed point
• Circumference: curve or the length of the curve
• Chord: line segment with two end points on the circumference
• Radius: line segment joining the centre to any point on the circumference
• Diameter: chord passing through the centre.

Remarks:

1. The length of a radius is half that of a diameter.
2. A diameter is the longest chord in a circle.

Properties of Circles

The important basic Properties of Circles are as follows:

• The diameter of the circle divides it into two equal parts.
• The diameter of a circle is considered to be the longest chord of the circle
• Circles which have equal radii are congruent to each other.
• The diameter of the circle is the largest chord and is double the radius.

Scratch Program to calculate Area and Perimeter of Square

Scratch Program to calculate Area and Perimeter of Square: To do this, we need to follow these steps

Step 1 : Formulas Related to Circles

The Circle Formulas are expressed as,

Diameter of a Circle	It is twice the length of radius	D = 2 × r
Radius of Circle	It is a half of diameter	r = D/2
Circumference of a Circle	It is the distance around the circle	C = 2 × π × r
Area of a Circle	Area of the circle describes the amount of space covered by the circle.	A = π × r2

Where,

r the radius of the circle.
d the diameter of the circle.
C circumference of the circle.
A Area of Circle

Step2: A circular ground has a diameter of 800 m. Calculate the circumference and area of the circle.

Where,First we have to find radius of the circle as, R = D/2, i.e R = 800/2, R = 400 m Area of circular ground, A = π × R2, = π × (400)2, = 22/7 × 400 × 400, = 502857.14 sq m Circumference of circular ground C= 2 × π × R, = 2 × π × 400, = 2 × 22/7 × 400, = 2514.28m

Step 3: Procedure

First Define Variable: three variables identified for this scratch program. I will list them here:

1. R = Radius
2. D = Diameter
3. A = Area
4. C = Circumference

Note: π = 22/7 = 3.145

• From Events, Drag green flag() block on sprite area.

• Click on the “variables” tab (top left), and click  “Make a variable”. Now type “Radius =R”, in the  dialogue box.
• Repeat this, and create a ‘Circumference =C’, ‘Area = A’ , “Diameter = D’ variable.
• From Variables, Drag the set() block ‘set variable to 0’ Initialize ‘D’ variables to 0 (eg : my variable = s)
• To Replace 0 value from your value in set() block where variable is ‘D’.
• From Sensing, Drag the ask() block , Change text and asks the user to ‘Radius of Circle′.
• From operator, Drag a divide() block and replace 0 value from this divide block with variable into set() block.

• From looks block, drag a say() block stays for the specified amount of time and replace text ‘hello’ from variable
• Repeat previous three process for variable (Area, Circumference).
• When the green flag is clicked, the script activates.
• To run the program. You should get the following result.

Input and Output