(upbeat music) - Oh, good morning, mathematicians.

I hope you are having an amazing day so far.

I have been working on this model sailboat for the past few days because our town is hosting a sailboat race.

Some of the other teachers are planning to race too.

Well, while we were building our boats, we started talking about the triangular shaped sails and I challenged the other teachers to see if they could name the triangles, and they did a great job remembering the properties that give triangles their names.

Do you know that there are actually many different types of triangles?

Well, I think I'm almost finished here so let's look at some examples, and then we'll see if you can name these triangles.

Now first, remember, a triangle is a polygon with three sides, three angles, and three vertices.

When we talk about naming and classifying triangles, we do that based on the lengths of their sides or the measure of their angles.

Take a look at the different types.

First, let's look at triangles based on their sides.

If all three sides measure the same length, then the triangle is equilateral.

If only two sides measure the same length, the triangle's isosceles, and if all three sides measure different lengths, the triangle is scalene.

Now let's look at triangles based on their angles.

If all three angles measure less than 90 degrees, the triangle is acute.

If one angle measures exactly 90 degrees, the triangle is right.

And if one angle measures greater than 90 degrees, the triangle is obtuse.

Okay, so let's see if we can name a triangle.

Look at this boat sail.

Can you help me classify the triangle?

First, let's use a ruler and we're going to measure the sides.

Okay, the bottom side is six inches, this side is eight inches, and this long side is 10 inches.

Okay, all different lengths, so what kind of triangle is this?

Scalene!

Yes, great job.

Now let's use a protractor and we're going to measure the angles.

Set the protractor right at the vertex point.

And look, this measures exactly 90 degrees, so we're already done.

What kind of triangle is this based on its angles?

A right triangle.

Great job.

Hey, what about this triangle over here on the board?

Let's use a yard stick and measure the sides.

I'm measuring 35 inches, 30 inches, and 30 inches.

So two sides measure the same.

This is isosceles.

Now let's use a protractor and measure the angles.

55, 55, and 70.

All three angles measure less than 90 degrees, so the triangle is isosceles and acute.

That's all the time that we have for today, mathematicians, and I've got to get off to this boat race.

Wish me luck.

Bye!