Is it possible to find the angles in this rather special isosceles triangle?
Here is a selection of different shapes. Can you work out which ones are triangles, and why?
Can you sketch triangles that fit in the cells in this grid? Which ones are impossible? How do you know?
Join pentagons together edge to edge. Will they form a ring?
This problem shows that the external angles of an irregular hexagon add to a circle.
Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?
Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?
Interior angles can help us to work out which polygons will tessellate. Can we use similar ideas to predict which polygons combine to create semi-regular solids?
