How to Identify Standard Geometric Polygons and Solids – Algebra Tips

In this video we’ll identify several
standard geometric polygons and some solids. First of all the polygons in in
orange here and these are all called regular polygons and the reason these
are called regular polygons is because all the sides are the same same length
as well all of the interior angles are the same. So you can conceive of drawing
a four-sided figure that had the same length sides like a diamond but all of
this the angles might not be the same and that would be called a diamond not a
square and it’s not a regular polygon unless the interior angles are the same.
Also you can conceive of drawing many different triangles but it’s only a
regular polygon if all of the side lengths are the same and the interior
angles are the same so we have triangle and square. What about as we go on
further with the polygons? Well we have a naming convention where we start with
the root, the prefix, that means the number of sides. So for something that
has five sides we start with that prefix Penta- which means five and then -gon,
-agon. So all of these are going to end with this this suffix -agon. For a
six-sided figure well the word the prefix to mean six is hex- so this is a
hexagon and set for seven sided figure we have hept- like you may have seen in
the in the Olympics the the heptathlon that’s that’s the women’s event where
they have seven events and a the men’s event has the the decathlon where they
have ten events. So the heptagon has seven sides. We’ve all seen stop signs
hopefully we haven’t gone through them and that is eight sides. There’s a stop
sign just rolled on its side slightly. The octagon you might remember that
because an animal in the sea that has eight arms is an octopus
so that we have that oct- that octa- prefix. Now for the last ones we don’t
have it memorized in our pocket as well but I’m going to give them to you anyway
and that for a nine sided polygon this is called a nonagon and I mentioned
earlier about the heptathlon and the decathlon well for a ten sided figure
you may have already guessed it that is a decagon because dec- means 10. I’ve
skipped 11 here because I want to get to 11 a 12 sided figure and this shows
up in trivia questions so I I wanted to give it to you. A 12 sided polygon,
regular polygon is a dodecagon and there are naming conventions I go on
further and further. You can see if we added more and more sides it gets very
close to a circle but never perfectly a circle if it has as long as it has some
flat sides even a million even a million flat sides would not be called
a circle. It would be some version of millionagon. Now what about the solids
here? I have eight solids here five of them are what we would call prisms or
what we do call prisms. Prisms meaning you have two opposing faces that are the
same. So here we have a top and the bottom two opposing faces that are the
same and then you’ve got these sides that come up that connect these two
opposing faces. And for this one, for the naming of the prisms, we call it by what
the opposing faces are and these opposing faces are triangles so this
would be a triangular prism. And the next one, well the opposing faces are
rectangles so this is called a rectangular prism. Now for this one when we have opposing
sides of squares we don’t call it a square prism we call it a cube. A cube –
something a magician would jump into for some kind of magic trick. Next see if you
can guess this one. The opposing sides that are the same are pentagons so this
is a pentagonal prism. And lastly I I bet you have already guessed this last one the
opposing sides are hexagons and so therefore this is called a hexagonal
prism. Okay all the prisms notice have all flat faces. All of the faces are flat
whereas the cone and the cylinder and the sphere you’ve got some curved faces
so like these cannot be called prisms unless they have all flat faces. So let’s
name this the cone you’ve seen an ice cream cone and and a snow
cone well those are all called cones so it’s a nice to be able to memorize when
you see it in a geometry format that is just called a cone just like you when
you’re having a good time in the summer. The next one is called a cylinder and
some of you may think about cars – I certainly like to think of how many
cylinders a car has. Well this is what they are. They’re a circle on one side
and a circle on the other side and then connected by this curved wall all the
way around. Now we we call it a cylinder you might also see it called a right
circular cylinder but nevertheless it is called a cylinder. And then the most our
most favorite sphere of all, of course, Earth – this is our sphere. Now Earth is
not a perfect sphere – some some geologists and astronomers would be
quick to tell you that the Earth is not a perfect sphere and
it isn’t – it’s a little bit oblong but but it gives it gives you a very good
idea – round the ball that is perfectly around would be a sphere. And actually
the Earth is very smooth by the way its surface if you shrunk it down to the
size of a pool ball it would be actually smoother than that pool ball but more
than you needed to know about some standard geometric polygons and solids.

One thought on “How to Identify Standard Geometric Polygons and Solids – Algebra Tips

  1. I'd be careful. There is such a thing as square prisms. If the two faces are squares, but the sides connecting them form rectangles, that is not a cube. A cube must have 6 square sides, not just 2 square faces

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