Constructions and Tilings — Class 7 Mathematics

This chapter develops precise geometric constructions using only an unmarked ruler and a compass, then explores tilings of the plane. You learn to construct the perpendicular bisector of a segment (justified by congruent triangles, since any point equidistant from the two endpoints lies on it), a angle at a point on a line, and to bisect any angle using the SSS congruence of two triangles. From these you build , , and angles, copy a given angle exactly, draw a line parallel to a given line, and construct a regular hexagon (made of six congruent equilateral triangles, since six angles fill the around a point). Ancient Shulba-Sutra rope methods are highlighted. In tiling, you ask which grids can be covered by tiles without gaps or overlaps, using a clever black-and-white colouring argument to prove some regions cannot be tiled, and you see how squares, equilateral triangles and regular hexagons can tile the entire plane.