Why is a triangle the strongest polygon?
because you can’t just change one of the angles or one of the side lengths without breaking the triangle. All the angles and sides re-inforce each other. Image a square made out of sticks that are attached loosely at the corners. You can squish two of the corners together to make a diamond shape, and you haven’t changed the length of the sides. But if you have a triangle made out of sticks, you can’t change it’s shape without destroying it.