CIRCLES - 4.6 ( 21-5-20)

Good morning students !😊😊

Welcome Back!! 

Today, we are going to recall some basic geometrical concepts which you had learnt in your previous classes.

At the end of the class, you will be able to:

➤ define and explain the concept of Circle.
➤ identify the different parts of a circle 

➤ illustrate a circle and the terms related to it : Centre, Radius, Chord & Diameter.
➤ 

CIRCLE

A circle is a shape with all points the same distance from its center. A circle is named by its center. Thus, the circle to the right is called circle A since its center is at point A. Some real world examples of a circle are a wheel, a dinner plate and (the surface of) a coin.

DIAMETER

The distance across a circle through the center is called the diameter. A real-world example of diameter is a 9-inch plate.

 RADIUS

The radius of a circle is the distance from the center of a circle to any point on the circle. If you place two radii end-to-end in a circle, you would have the same length as one diameter. Thus, the diameter of a circle is twice as long as the radius. 

CHORD

A chord is a line segment that joins two points on a curve. In geometry, a chord is often used to describe a line segment joining two endpoints that lie on a circle. The circle to the right contains chord AB. .

LET'S WATCH A VIDEO TO UNDERSTAND THE DIFFERENT PARTS OF A CIRCLE OR click on the link 👉 https://youtu.be/CTDtiXHorgc

It turns out that a diameter of a circle is the longest chord of that circle since it passes through the center. A diameter satisfies the definition of a chord, however, a chord is not necessarily a diameter. This is because every diameter passes through the center of a circle, but some chords do not pass through the center. Thus, it can be stated, every diameter is a chord, but not every chord is a diameter.

REGIONS OF A CIRCLE

A circle divides the plane into three parts:

1. the points INSIDE the circle (interior).
2. the points OUTSIDE the circle (exterior).
3. and the points ON the circle

POINTS INSIDE THE CIRCLE

POINTS OUTSIDE THE CIRCLE

POINTS ON THE CIRCLE

Watch this video or click on the link to understand this concept 

👉 https://youtu.be/Ay5r0y4fSUw

Now, Let's Start Ex-4.6 (page no.84)
Q2: (a) Is every diameter of a circle also a chord?
       (b) Is every chord of a circle also a diameter?


Solutions:(a) Yes, every diameter of a circle is also a chord. Diameter is also called as longest chord.
(b) No, every chord is not a diameter because every diameter passes through the center of a circle, but some chords do not pass through the center.


Q4:  Say true or false:
(a) Two diameters of a circle will necessarily intersect.
(b) The centre of a circle is always in its interior.


Solutions:
(a) True, two diameters will always intersect each other at the centre of the circle.
(b) True, the centre of the circle will always be in its interior.


That's all for today
Take Care
God Bless!!