Introduction - Triangle and Its Properties, Mathematics, CBSE Class 7 Video Lecture

hello friends this video on triangle and
its properties Batman is brought to you
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topics to be covered in this lesson our
introduction medians of the triangle
altitudes of a triangle and then some
property of tramble exterior angles of a
triangle types of triangles wherein we
will discuss scalene triangles isosceles
and equilateral triangle property of
lengths of sides of triangle
right-angled triangle and Pythagoras
theorem triangles what are they and
where do we see them think of a hut
which you often use to draw when you're
a kid so anyway I asked you to draw a
heart
you were very eager to draw him somewhat
like this now when you look at the upper
portion of the heart this is nothing but
a triangle what it is how does it look
like it looks like a closed shape which
has three sides so this is one side this
is the other side and this is the third
side so you have a shape a closed shape
bounded by three sides that's a triangle
you look at the pyramids the picture of
pyramids which you would have definitely
seen in your books or on television now
when you look at this pyramid you get
the shape of a triangle you see this is
how a triangle looks like even for the
smaller ones you get to see the shape of
a triangle think of a situation where
you want to climb up the ladder to reach
out to something on the upper shelf now
when you place your ladder so do you see
triangle anywhere you might be thinking
that no I really do not see a triangle
but there actually is a triangle in this
situation as then just think of it
somewhat this way when you look at it
you look at this entire thing where you
have a wall and you have a ladder and
when you look at the Odin
nation from one side of it what do you
see you again see a triangle so the
ladder the wall and the ground they're
together form a triangular shape again
even the arrow in the game which you
play right just to check whether you
shot the arrow at the right point or not
so then you closely look at this arrow
so there also you encounter a triangle
since a small small things around us we
see triangles we use triangles so
triangles are a very are one of the
common shapes that we come across in our
day-to-day life so what exactly is a
triangle the name itself says try angle
triangles three so basically it is
something with it is a geometrical shape
with three angles so it is basically a
polygon with three sides so three sides
therefore three angles what does a
polygon a polygon is a figure which is
closed which is formed only by line
segments so here you can say this is a
closed polygon that is you have line
segments forming a closed structure and
how many sides do you have you have
three sides now when you look at this
triangle on the picture this is normally
represented in this fashion triangle ABC
so we do not write the word triangle
instead we just put this symbol of a
small triangle and then we write ABC now
the basic elements of triangles are
sides angles and vertices so when we say
sides so what are the sides for this
triangle so a b b c and easy these are
the three sides of the triangle a B BC
and AC next are the vertices so whatever
toises vertices are those points where
the silence meat for example point a so
a is a vertex so at a BA and
see a they both meet similarly at B a B
and C B they meet
similarly ac and BC they meet at Point C
there are four points a D and C are the
vertices of the triangle and then a
third element that is angle and which
other angles and will tell us the
orientation between the sides for
example this angle a which can also be
named as angle B AC this shows the
orientation between a B and a C
similarly this angle B shows the
orientation between a B and BC so this
can be written as angle ABC similarly
this angle which can be written as ankle
a CV they shows the orientation between
AC and DC so all in all there are six
elements which define a triangle what
are those six elements threes so all in
all there are some nine elements which
you know kind of determine load which
specifies a triangle three sides three
vertices and three angles now a couple
of other things are for this angle B AC
let's say this is BAC so for this
particular angle which is the opposite
sign so the sign located opposite to it
it means that side which doesn't
participate in the formation of this
angle so for angle BAC if you take
example of DAC for this angle the
opposite side would be be C similarly if
you talk about angle ACB which one would
be the opposite side so which is the
side which is committed to angle ACB is
this side that is a similarly if you
take example of any side let's say if
you talk about side is so for AC this is
the side AC which is the opposite angle
so the opposite angle
in this angle so far I see the opposite
angle would be angle ABC similarly for a
B which one would be the opposite angle
this is a V so the opposite angle
building angle C so for a B opposite
angle would be angle ACB so these are
some of the very common properties or
the basics of a triangle thank you
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