What’s the difference between the following shapes? How to tell the difference between equilateral, scalene and isosceles triangles?
The easy (and right!) answer is that there is NO difference! They are all triangles! Each shape has three sides: “tri” meaning three. It’s as easy as counting One, Two, Three.
But let’s say your teacher throws a zinger. She wants to know which triangles are equilateral. Which are scalene? And which ones are isosceles?
Huh?
Don’t let the fancy words throw you off. It’s just a fancy way of putting the triangles into categories.
The easiest way to categorize triangles is by comparing the three lines that make up the triangle. If this doesn’t make sense, it might be a good idea to get some math homework help.
If a triangle has three equal lines, with each one having the same length, the triangle is equilateral. That means “EQUAL SIDES!” Pretty easy to remember, right?
Here’s an equilateral triangle, where all the sides (letter a) are the same.:
The other two, isoscele triangles and scalene triangles can be easy to figure out from here, especially with some geometry help from an online math tutor. If a triangle has TWO sides that are the same, but the third side is different, it is isosceles. This comes from the Greek word “iso” which means “equal” and “skelos” which means “leg.” So think of it as a person standing up, where her two legs are equal lengths, while the floor has a different length.
A triangle where EVERY side is different is a SCALENE triangle. This from Greek as well. The word SKALENOS means “uneven.” What’s a good way to remember skalene? There’s no easy way, but maybe think of an imbalanced scale?
Let’s recap:
It can get a little more complicated when we start looking at the insides of triangles and calculating their angles. But let’s save that for another day. To do that you will want to check out our article on the 45-45-90 triangle.