The sum of angles in any plane triangle is 180 o .
All edges are equal, except for the long edge of the trapezoid.
You may want to make a pattern block template out of a piece of cardboard. Tessellations by polygons Recall that a tessellation of the plane by polygons is a collection of polygons that cover the plane without gaps or overlaps. The polygons are not necessarily congruent, and they do not necessarily make a repeating pattern. Here are two special types of tessellations. So the type of each vertex in a checkerboard is 4.4.4.4.