Wednesday, 12 July 2017

Circle I – What is a circle? Definitions, Formulae and Different Parts of a Circle

In this post, we will discuss what is a circle and definitions, formulae and different parts of a circle from Euclidean Geometry that will help you save time in SSC CGL 2017
What is a circle
Topics from geometry play an important role in SSC CGL 2017. One such topic is Circles. The properties of circles are confusing. This blog will help you simply all the confusing properties of a circle and help you solve questions quickly and efficiently. Hence helping you save time in SSC CGL 2017.

This is the first post in the series of Circles. In this post, we will discuss what is a circle? definitions, formulae and different parts of a circle, which will help you solve questions that come from the topic of circles in SSC CGL 2017.

What is a circle?      

A circle is a round shaped closed plane figure. A circle is a collection of points and all these points are equidistant from a given point known as the centre.
What is a circle

Radius (r) – The line from the centre of the circle to the circumference of the circle is called as radius which is denoted by 'r'.

What is a circle

Diameter: The line that touches 2 points of the circumference and passes through the centre of the circle is called as Diameter', denoted by 'D'.


D = 2r 

What is a circle

Circumference - The boundary of the circle is called as Circumference. The circumference of the circle can be measured by using 2πr or πd formula, where π = 22/ 7.

What is a circle

Area: The area of a circle can be measured by using πr² or πd²/ 4 formula, where π = 22/ 7.

What is a circle

Arc – Arc is a part of the circumference.

The smaller arc is called as a minor arc and the larger arc is called as a major arc.


What is a circle

How to measure the length of the arc?

The length of the arc can be measured on the basis of the concept proportionality. 

The total angle in the circle is 360°.
An arc will make angle θ at the circle. Hence, the length of the arc can be measured using the given formulas below 
What is a circle
What is a circle

Sector: A sector is a combination of 2 radii and a minor or a major arc. 

What is a circle
The area of the sector can be calculated with the help of the given formula.
What is a circle

Segment: A segment is a part of a sector which is formed after subtracting the triangle from the sector.  

What is a circle
Area of a segment can be calculated by using the below formula, 
What is a circle

Chord: A chord is a straight line joining any two points in the circle.

What is a circle


Tangent: A Tangent is a line that touches the circumference of the circle at a point.  


What is a circle

This was the basic introduction to the topic of circle. Do write in the comment section below how this blog has helped you understand, what is a circle? - Circle Definitions, Formulae and different parts of a circle.

Stay tuned for more on different parts of a circle and download free E-books for practice questions.  
What is a circle
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