Originally Posted by
HomekeepingGran
So the Recs ruler lets you divide a rectangle into triangles? (And thanks for reminding me Amazon is there. I may do some ruler shopping before long. I don't know why I didn't think of it because I shop there all the time.)
Not exactly. The tri-recs ruler is actually a set of 2 rulers. They let you make a "squared triangle" or a "triangle in a square" unit, which is square. There's not a standard name for this unit. In the photo that RainyBC provided, it's the teal and white unit in the bottom row right under the purple square . The ruler is needed because the angles are hard to achieve (63.44, 63.44, and 53.13 degrees for main triangle) A rectangle is a 4 sided shape where all the angles are 90 degrees, so a square is actually a special kind of rectangle. End of geometry lesson for today. There will be a quiz tomorrow.