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A tessellation or a tiling is a way to cover a floor with shapes so that there is no overlapping or gaps. Tessellation Remember the last jigsaw puzzle piece you put together? Well, that was a tessellation. The shapes were just really weird.

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Brick walls are tessellations. The rectangular face of each brick is a tile on the wall. Examples Chess and checkers are played on a tiling. Each colored square on the board is a tile, and the board is an example of a periodic tiling.

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Mother nature is a great producer of tilings. The honeycomb of a beehive is a periodic tiling by hexagons. Each piece of dried mud in a mudflat is a tile. This tiling doesn't have a regular, repeating pattern. Every tile has a different shape. In contrast, in our other examples there was just one shape. Examples

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Alhambra The Alhambra, a Moor palace in Granada, Spain, is one of today’s finest examples of the mathematical art of 13th century Islamic artists.

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Regular tiling To talk about the differences and similarities of tilings it comes in handy to know some of the terminology and rules. We’ll start with the simplest type of tiling, called a regular tiling. It has three rules: 1)The tessellation must cover a plane with no gaps or overlaps. 2)The tiles must be copies of one regular polygon. 3)Each vertex must join another vertex. Can we tessellate using these game rules? Let’s see.

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Tessellations with squares, the regular quadrilateral, can obviously tile a plane. Note what happens at each vertex. The interior angle of each square is 90º. If we sum the angles around a vertex, we get 90º + 90º + 90º + 90º = 360º. Regular tiling How many squares to make 1 complete rotation?

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Which other regular polygons do you think can tile the plane? Regular tiling

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Triangles? Triangles The interior angle of every equilateral triangle is 60º. If we sum the angles around a vertex, we get 60º + 60º + 60º + 60º + 60º + 60º = 360º again!. Yep! How many triangles to make 1 complete rotation?

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Will pentagons work? Pentagons The interior angle of a pentagon is 108º, and 108º + 108º + 108º = 324º.

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Hexagons? Hexagons The interior angle is 120º, and 120º + 120º + 120º = 360º. How many hexagons to make 1 complete rotation?

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Heptagons? Octagons? Heptagons Not without getting overlaps. In fact, all polygons with more than six sides will overlap.

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So, the only regular polygons that tessellate the plane are triangles, squares and hexagons. That was an easy game. Let’s make it a bit more rewarding. Regular tiling

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A semiregular tiling has the same game rules except that now we can use more than one type of regular polygon. To name a tessellation, work your way around one vertex counting the number of sides of the polygons that form the vertex. Go around the vertex such that the smallest possible numbers appear first. Here is an example made from a square, hexagon, and dodecahedron: Semiregular tiling

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There are only 8 semiregular tessellations, and we’ve now seen two of them: the 4.6.12 and the 3.3.4.3.4 Your in-class construction will help you find the remaining 6 semiregular tessellations. Here is another example made from three triangles and two squares: Semiregular tiling

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If the arrangement at each vertex in a tessellation of regular polygons is not the same, then the tessellation is called a demiregular tessellation. The 3 regular tessellations (by equilateral triangles, by squares, and by regular hexagons) and the 8 semiregular tessellations you just found are called 1-uniform tilings because all the vertices are identical. Demiregular tiling If there are two different types of vertices, the tiling is called 2-uniform. If there are three different types of vertices, the tiling is called 3-uniform.

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Examples 3.4.6.4 / 4.6.123.3.3.3.3.3 / 3.3.3.4.4 / 3.3.4.3.4 There are 20 different 2-uniform tessellations of regular polygons.

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Summary Regular Tessellation –Only one regular polygon used to tile Semiregular Tessellation –Uses more than one regular polygon –Has the same pattern of polygons AT EVERY VERTEX Demiregular Tessellation –Uses more than one regular polygon –Has DIFFERENT patterns of polygons used at vertices –Must name all different patterns.

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Name the Tessellation Regular?SemiRegular?DemiRegular? SemiRegular4.6.12

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Name the Tessellation Regular?SemiRegular?DemiRegular? Demiregular3.12.12/3.4.3.12

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Name the Tessellation Regular?SemiRegular?DemiRegular? Demiregular 3.3.3.3.3.3/3.3.4.12

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Name the Tessellation Regular?SemiRegular?DemiRegular? DemiRegular3.6.3.6/3.3.6.6

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Name the Tessellation Regular?SemiRegular?DemiRegular? SemiRegular3.3.4.3.4

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REGULAR POLYGONS … have 3 or more sides. have 3 or more angles. all sides are equal. all angles are equal.

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A REGULAR TESSELLATION is … a tessellation made up of congruent regular polygons. REMEMBER … Regular polygons are polygons that are the same size and shape. Regular means that the sides are all the same length.

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Lesson 9-4 Tessellations. 5-Minute Check on Lesson 9-3 Transparency 9-4 Click the mouse button or press the Space Bar to display the answers. Identify.

Lesson 9-4 Tessellations. 5-Minute Check on Lesson 9-3 Transparency 9-4 Click the mouse button or press the Space Bar to display the answers. Identify.

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