- Books Name
- class 7 Mathematics Book
- Publication
- ReginaTagebücher
- Course
- CBSE Class 7
- Subject
- Mathmatics
Circumference of a circle
Circle radius,diameter and chord
The segment joining the center to a freely chosen point on the circumference is called the radius. We usually denote radius by the lowercase r or the uppercase R.
The segment that joins the two points of the circle is called a chord.
The chord passing through the center of the circle is called the diameter.
AO=BO=EO=FO as circular radii.
The radii EO and FO form the diameter EF.
BC is a chord.
Parts of the circle
Diameter of Circle:
The distance across the circle. The length of any chord passing through the center. It is twice the radius.
Diameter = 2⋅Radius = 2r
Radius of circle:
The radius is the distance from the centre to any point on the circle.
Radius is also known as half of the diameter.
Radius=Diameter/2
Chord:
The segment that joins the two points of the circle is called a chord.
A circle
Compass can look different, but all whips have two legs - a sharp-pointed pin and a pencil.
Compass can be used to draw a circle.
If you mark a small mark or dot on a piece of paper and place the sharp crank leg at that point, you can draw a circle. The dot is called the center of the circle, and we usually denote by the capital letter O.
The segment joining center O of a circle to a point on the circle (point A in the drawing) is called the radius.
Circle circumference
Circumference of a circle is the actual distance around it.
Ratio of the circumference and the diameter of a circle is a constant
The numerical value of π is taken as (frac{22}{7}) or 3.14. (approximate)
Circumference of a circle = 2πr, where r is the radius of the circle
All circles are similar to one another. So, the ratio of the circumference to that of diameter is a constant,
That is CircumferenceDiameter=constant(piπ)
Therefore Cd=π (Where the approximate value of π is 3.14)
C= d⋅π or C= d⋅3.14
The diameter is twice the radius (2r), so the above equation can be
written as C=2r⋅π Note: d=2r
Therefore, the circumference of a circle, C=2πr units.
Position of two circles in a common point
- The circles have no common points, and they are inside each other.
- The circles have one common point, touching them externally.
- The circles have one common point (B), and they touch internally.
- circles have no common points, and they are off each other