Regular tessellations use identical regular polygons to fill the plane. The polygons must line up vertex to vertex, edge to edge, leaving no gaps.
Semi-regular tessellations have two properties:
• They are formed by two or more types of regular polygon, each with the same side length
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• Each vertex has the same pattern of polygons around it.
There are 8 semi-regular tessellations in total. We know each is correct because again, the internal angle of these shapes add up to 360.
For example, for triangles and squares, 60 × 3 + 90 × 2 = 360.
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