I was looking for a simple triangle foldable this evening and couldn't find one. This is what I created, so you don't have to. The students cut around the foldable on the dotted lines, and they write down the definitions/examples after they glue in their foldable.
There are spaces for the definition, equilateral, isosceles, and scalene triangles. I also used font visuals for those visual learners.
PS - Fits well into the black & white speckled notebook with room for a heading/title/footer in your journal.