About this video
The video draws a right isosceles triangle whose two equal sides have length 3, placing the 90-degree angle between them. It then explains that, because the angle and the two side lengths are fixed, the third side is forced, so there is only one unique triangle that meets the conditions.
You'll be able to
- draw a right isosceles triangle with two given equal sides.
- explain why fixing an angle and the two sides around it gives a unique triangle.
Key words
- right triangle
- A triangle with one 90-degree angle.
- isosceles triangle
- A triangle with at least two sides of equal length.
- unique triangle
- The only triangle (apart from moving or turning it) that fits the given conditions.
Transcript
They're asking us to draw a right triangle. So that means it has to have a 90-degree angle. But it's also an isosceles triangle, so that means it has to have at least two sides equal and has two sides of length 3. So those two sides that are going to be equal are going to be of length 3, and it's got to be a right triangle.
So let's see if we can do that. So let's try to make this right over here the right angle. And let's make this side and this side have length 3, so 3 and then 3 right over there. Let me make sure I get that right angle right. OK, there you go. So it's a right angle.
It's isosceles. At least two sides are equal. And the two sides have length 3. So it seems like we've met all of our constraints. Now they say, is there a unique triangle that satisfies this condition? So another way of rephrasing that, is this the only triangle that I could have drawn that meets these conditions?
Well. I can't change this angle if I want to meet these conditions. I can't change these two lengths. And if you keep this angle constant and you keep these two lengths constant, then this point and this point are going to be there are no matter what. So this is the only side that can connect those two points.
So this is the only triangle that meets those conditions. You can't have different side lengths, or you couldn't have different angles right over here and also meet those conditions. So is there a unique triangle that satisfies the given conditions? Yes, there's only one unique triangle.
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