A triangle is the ONLY two dimensional polygon that cannot collapse or bend — it is surprisingly strong for its simple shape. That’s its beauty — all 3 sides work together to find strength. A square – -a shape with just one more side — doesn’t have this strength. It will easily bend or collapse.
The triangle is well known to engineers who use it ubiquitously in our world because of its elegance and surprising strength. You can’t walk down the street without seeing triangles just about everywhere.