Sector of the circle

 sector - 

sector is an area surrounded by two radii and an arc, as shown is figure.

OA and OB is radius and AxB is arc

Area of sector = 

Perimeter of sector =  

https://www.youtube.com/playlist?list=PLBmAAJV4jp1bS_cT9coruDYn27p2wYPQX

 

 

 

 

 

 

Circumference of circle

 

Circumference of circle- length of the boundary of a circle or perimeter of  a circle is called circumference.

circumference of a circle = 2𝞹r  (where 𝞹 = 22/7 and r = radius)

chord of a circle

 

Chord of a circle- Line joining the two points of a circle is called chord.

AB, CD, EF are chords 

Diameter of a circle- A line (chord) that passes through the centre of the circle is called diameter of circle.Diameter is the longest chord.

Radius of the circle

 

Radius of the circle- If we construct a line which join centre of the circle to the any point of boundary (circumference) of the circle. Generally we denote radius by r .

OA,OB. OC OD are radius of circle

Definition of the circle and important terms related to the circle

 

circle

Definition of circle - Circle is the set (group) of all those points which is equidistant from a fixed point.

this fixed point is called the centre(O) of the circle.

 Concentric circle-  (संकेंद्रित वृत्त)

If two and more then two circle have same centre but different radii, they are called concentric circles.

यदि दो या दो से अधिक वृत्तों का केंद्र समान लेकिन उनकी त्रिज्याएँ भिन्न-भिन्न हों , उन्हें संकेंद्रित वृत्त कहते हैं।

concentric circles

blue, green and red are three concentric circles as they have same centre but different radii 
नीला, हरा और लाल तीन संकेंद्रित वृत्त हैं क्योंकि उनका केंद्र एक ही है लेकिन त्रिज्या अलग-अलग है

three different arrows show different radii of the circle                             तीन अलग-अलग तीर वृत्त की अलग-अलग त्रिज्याएँ दिखाते हैं