Examples: Quadrilaterals and Circles Video Lecture - Class 6

hello friends this video on basic
geometrical ideas part 21 is brought to
you by exam furor calm no more fear from
exam so now that we have discussed most
of the concepts of this lesson let us
quickly look at some of the questions
question number one draw a rough sketch
of a quadrilateral PQRS ok let's let's
draw simultaneously let's say we have
drawn a quadrilateral quadrilateral
means four sides and the vertices should
be P Q R and s draw its diagonals what
are diagonals the lines which joins non
adjacent vertices so which are non
adjacent vertices for P is a non
adjacent vertices so we join P and our
similarity which is the non adjacent
vertex for Q it is nothing but s so we
join Q and s so P R and s Q are the
diagonals so named them so what are the
diagonals diagonals are P sorry
diagonals would be P R and Q s so these
are the diagonals is the meeting point
of the diagonals in the interior or
exterior of the quadrilateral where do
the two diagonals meet they meet at this
point let us call this point as ho so
what do you think t o is located inside
the quadrilateral or outside because
this is the quadrilateral should always
definitely located inside
so therefore o is in the interior of the
quadrilateral question number two
identify three triangles in the figure
so if you look at this figure you see a
lot of you can actually see multiple
triangles here so what are the multiple
triangles one time that is travel ABC
the bigger triangle the other triangle
would be tangle in DB the smaller one
this one and the third one would be the
still smaller one which is ABC so this
is one triangle this is neither kanga at
the
your mother's another triangle so that's
our part A Part B write the names of
seven angles know which are the angles
involved here
this is one angle this is the other
angle this is another so we have three
angles here this is one angle this is
one angle this is one angle so we have
three angles here so let us start naming
the angles as well so this would be
angle a B D and with a DB and a DC an
angle is C D so basically we have
covered this this this and this so we
have covered this four angles next to be
will cover and lvad angle B is C so B
and E is this angle and B is C is this
angle but this is also another angle and
so what are we left with we are left
with angle D ay C that is the same so
that's how we have covered all the seven
angles see write the names of six line
segments so what are the various line
segments in one two - a B next is BD
next is T C now BD is one line segment
BC is one line segment but BC also is
one line segment the total one though BC
is a combination of BD plus DC but BC is
a separate line segment right is the ad
so these are the six line segments D
which two triangles have angle B as
common now we have three triangles three
is the total possibility of triangles
now out of these three triangles which
two am triangles have angle B so
triangle ABC yes it has angle B triangle
ADB yes it also has angle B but what
about our triangle ABC
triangle ABC this triangle doesn't have
angle B so therefore the answer would be
triangle ABC and triangle adb question
number three from the figure identify
the center of the circle which is the
center obviously o because this is the
point from there all the points of the
circle are equidistant three radii so
what are the three ready hey that you
can see here OC because it is connecting
two connecting the center to a point of
the circle
similarly o a because this is also
connecting a point e on the circle to
the center and OB so o8 OB and OC are
the three red line a diameter so
diameter is nothing but twice the radii
so basically this is radius this is also
radius joining the two radii is the
diameter so basically AC is the diameter
a chord so diameter is also a chord but
other than the diameter do you have any
other part of course you have one Edie
because it joins two points on the
circle so Edie is afford other than the
diameter but otherwise standard is also
a chord two points in the interior so
which are the points which are located
inside the circle one point is P another
point is ho because st. it is also a
point which is located inside the circle
so oh and B are the two interior points
a point in exterior very clearly you can
see q a sector what is a sector size of
a pizza slice of a pizza has an arc and
two radii so this is the sector so you
can name it as au a B Oh a be a segment
segment is surrounded by a chord and an
arc therefore e d is a segment question
number four say true or false two
diameters of a circle will necessarily
meet yes that is definitely true that's
because if you have
or circle like this and you have its
center here now whenever you talk about
the diameter that diameter is going to
connect to opposite points and in order
to connect to opposite points it has to
pass through the center no matter where
ever you draw a diameter any diameter
you try to draw on the circle it has to
pass through them Center so it is really
necessary that the diameters will
intersect center of a circle is always
in its interior yes definitely there is
no doubt in that because even if you try
to imagine Center as an exterior point
just prove it that all the points of the
circle will be at equal distance from
the center that will never be possible
so the only position from there all the
points on the circle will be at the same
distance from the center is this
location of the center so the center
will always have to be in the interior
of the circle so with this we have
reached towards the end of this lesson
and I hope that this lesson on basic
geometrical ideas would have helped you
so this is where you start learning
about the basics of geometry now as you
go ahead to towards your higher classes
you learn more about these concepts only
so it is very important that you get
your concepts very very clear at the
stage itself so that when you go to your
next classes class 7 that 8 then you are
very much comfortable solving the
problems of geometry so with this we
will conclude this lesson see you all in
the next lesson thank you please visit
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