Nets of cones Video Lecture - Class 7

in this video we're talking about how to
draw Nets of right circular cone and
remember that when we talk about a net
we're talking about starting with a
three-dimensional object and
transforming it into a two-dimensional
shape and you can think about the
two-dimensional shape as the piece of
paper that you could fold up into this
three dimensional object so that
two-dimensional piece of paper is going
to be the net for this three dimensional
object we're going to be drawing Nets
for right circular combs and so we're
going to start with a cone and the fact
that we call it a right circular cone
means two things first of all circular
here or circle means that the base of
the cone is going to be a perfect circle
and the fact that it is a right circular
cone means that the angle between the
vertex of the cone and the center of the
base here so the angle between this line
here and the radius here this angle is a
90-degree angle or a right angle so it's
going to be a right circular cone and we
want to draw the net of it the easiest
way to draw a net for a right circular
cone is this way if we want to try to
make it somewhat precise we're going to
draw a circle first of all let's
indicate here the center of our circle
and we're going to draw a circle around
this center point so maybe our circle
looks something like that and then what
we want to do is go ahead and draw two
lines roughly like this coming from the
edge of the circle to the center of the
circle so we have two radius lines like
this and what we can do is then go ahead
and erase everything outside of this
section like so and what we're left with
this is going to be the lateral face or
the edge of the cone then all we need to
do is account for the base of the cone
and that again it's going to be another
Perfect Circle which we can just go
ahead and draw on the side over here and
just make sure that it touches this
portion that we drew earlier so what we
end up with then is the base of the cone
so if we go ahead and draw in the radius
here if we say this is about the center
and this is the radius if we want to
label its dimension so that we indicate
that this net represents this cone here
we can label the radius there with five
and then 13 was given to us as the slant
height so we'll
that also before we do let's go ahead
and copy this net so that we can use it
for our second cone over here but we're
going to have this first net and we want
to go ahead and label the radius with
five since we were told that the radius
of the base was five we were told that
the slant height is 13 so we can say
that this is 13 and this is also 13 so
this then would be the net of this right
circular cone and if we did another
example here we're given the radius and
the slant height we would draw the same
net and we would just call the radius 2
and the slant height here 10 and
obviously to be as accurate as possible
what we want to do is just make sure
that we draw that large circle such that
the radius here can be 10 and then in
this case draw a smaller circle such
that the radius is 2 and these
dimensions match up but in general
that's how you draw the net for a right
circular cone