Sector and Segment of a Circle Video Lecture - Class 6

hello friends this video on basic
geometrical ideas part 20 is brought to
you by exam feel calm no more fear from
exam now like how we had discussed in
case of polygons for circle also we will
talk about the interior and exterior
parts of a circle now in order to
understand the interior and exterior of
a circle let us imagine it in this way
now instead of circle let us imagine a
circular field or a circular part which
is like full of greenery Brussels plants
or you see that it is a park where it is
a lawn which is in the shape of a circle
so how will you tell me which part is
the interior of the lawn indeed in its
inside of the lawn definitely that part
which is like enclosed by the lawn which
is enclosed by the circle so basically
this entire greenery is the interior of
the lawn and anything that is located
out of it is considered to be the
exterior so let us consider any point so
let us consider these cows which are
grazing in this field
so where are depression are they present
inside the field or outside the field
obviously they are present inside the
field that is why they are breathing
there so they are present inside the
field that means they are in the
interior of the field now whereas there
are certain cows which are present
outside the field so that means these
are in the exterior of the circles these
points so if you have points here so
they are considered to be the exterior
points and if you have certain points
here these are considered to be Indian
points so in case you have a point which
is located exactly on the boundary then
it is said to be on the circle or it is
said to be on the boundary of the circle
so that's how we distinguish between
interior and exterior of a circle
circumference of a circle so now what is
circumference of a circle it sounds to
be a very big name circumference
difficult to remember also but the
concept is very simple circumference
nothing but the boundary of a circle now
I will tell you why do we need to know
the boundary of a circle you might ask
that okay fine
boundary of a circle why do we need to
know the boundary of a circle what what
will we get out of it so let me give you
this real-life scenario let us suppose
that there is a field which is circular
in shape now due to lot of disturbances
from outside maybe some notorious people
are entering inside the fees and
destroying the crops or some of the
animals are coming and grazing in inside
the field and destroying the crops so in
order to protect the field
what you decided is you are going to put
a boundary on the field some additional
boundary maybe with with wooden
platforms or with wires you are going to
fence they die Affinia so that it will
remain protected so that no disturbing
element can enter inside the field so
now you want to do this now in order to
do this you need some material you need
wires in order to you know bring do make
that boundary now when you ask somebody
to build that boundary for you that
person would need some material to build
the boundary either breaks or wires or
or wood something some material would be
needed now how will that person know
that how much material is needed because
that person needs to know that what does
the length of the boundary that needs to
be done so how do you know the length of
the boundary only then you measure the
length of this entire boundary and the
length of this entire boundary is what
we call as circumference so
circumference is the length of the
boundary of the circle now a smaller
circle like this if you have a small
field like this then the length is also
small it woman is this much when you
have a big field like this the length is
also big therefore the circumference is
bigger so a smaller circle will have a
smaller circumference a bigger circle
have a bigger circumference so sockets
has a very important practical
application and that is why we have
introduced a special term for
circumference
now as you put your higher classes you
will also learn how exactly to measure
the circumference of a circle because in
this entire lesson we are just
introducing you to the basics of
geometry we are just introducing you to
the terms so that you understand what
the circumference what is a circle what
is the center so you had aware of all
these terms so that in your earlier
classes when you actually learn how to
calculate circumference how to calculate
area that times your basics will be
clear and you'll be able to get more
knowledge so this is about circumference
so we will now learn about sector of a
circle what a sector now in in simple
English what do you understand by sector
however observed the term sector been
used in a lot of postal addresses where
we see sector 23 of Google or where we
see sector 105 of ragini so what does
that sector means that means that there
was a big area named maybe program and
we have divided that into small areas
and we call each area as a sector and we
have numbered them at sector 1 2 3 4 and
so on
so sectors are basically portions of a
bigger region so here also in a circle
sector is basically a portion of a
circle so you can very easily remember a
sector of a circle as a slice of your
pizza that's the best way to remember
what a sector is you do not need to
remember the definition you do not need
to remember any concept just to remember
sector is nothing but a slice of the
pizza how let's have a look at it what
do you see on the screen you see a pizza
with one slice being cut that you have
eaten that one slice of pizza so what
was that once Lance had this pizza being
intact before you eat that one slice you
had a complete pizza right so this one
slice what does it made up of it is made
up of one arc and two radii this is the
radius of the circle
because this is the center of your
circle so two radii and one arc makes a
sector so this slice of pizza which you
eat that is nothing but that is called a
sector of a circle so sector is the area
enclosed by an arc and a pair of radii
you can see is very distinct here two
radii that is a pair of radii and earn
an arc this is an art because portion of
a circle is called AK so this is
basically a sector of a circle now it is
you can divide a circle into as many
sectors as you want for example you have
this circle if this is your center so
this portion is the sector of a circle
similarly if I want to divide it into
another sector but this is a smaller
sector that is perfectly fine sector is
all about it has to be surrounded by two
radii and one arc that's it that's a
sector so this is called sector of a
circle now you might ask why do we need
to know about sector that is also
important because many times we come
across real-life problems where we need
to calculate the portion of a particular
field let's see that the same circular
field which I was considering in the
previous concepts let's say the same
circular field is getting divided into
different portions like it is getting
divided among six people like how open
circuit device gets divided into five
people in a similar way let's say that
the field is also getting divided into
five portions and everybody wants some
portion of the central part and some
portion of the far away part so that's
how everybody wants it's their wish so
you need to actually calculate the area
of each sector so that you are able to
divide the field accordingly so in a lot
of real-life problems you actually need
to calculate the same area of sector
that is why we need to know what the
sector of a server now the last
terminology is segments of a circle so
we understood sector now what a segment
let's see segment is basically the area
that is enclosed by an arc and a corner
now we already saw that cord is now
again let's do the same example let's
say the same field is now getting
divided into five people but this time
they do not want it like different
sectors they just wanted to get divided
into five parts so how would you divide
that for you so this is the field you
just divide it into five parts like this
part 1 part 2 part 3 part 4 part 5 so
that's how you divide it okay now in
this case what is this so this last
portion that you encounter that is
basically a segment where you have one
cord and one arc so instead of the two
radii in this case you just step one
cord because wherever you draw a cord in
a circle you basically divide the circle
into two parts because the cord is going
to join two points on the circle but the
moment you draw a call you think of any
circle you draw cord from here to here
you divide it into two parts this is one
part this is one part you draw a board
here you divide it into two parts one
part two part so any part will divide
the circle into two parts and each part
of the circle will be called a segmented
so segment is that area which is
enclosed by an arc and oh god so please
do not get confused with sector and
segment so the simplest way to remember
it is sector means
Sector 22 of goona and sector also means
the slice of the pizza so that's how you
can remember sector very easily thank
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