It categorizes triangles into equilateral, isosceles, scalene, obtuse, right, and acute based on their sides and angles. The video also covers the concept of congruency, demonstrating how two ...

A right-angled triangle has one angle that is exactly 90°. An obtuse-angled triangle has one angle that is greater than 90°. The triangles can be further classified as equilateral close ...

You can see one angle labelled 40º. This means the triangle cannot be equilateral, because each angle would need to be 60º. You can see that two of the sides are equal.

During this work, Schein came across the work of 20th century mathematician Michael Goldberg, who described a set of new shapes that have been named the Goldberg polyhedra.