RD Sharma Solutions for Class 7 Chapter 18 "Symmetry"- If a line divides a figure into two parts such that when the figure is folded about the line the two parts of the figure coincide, then the line is known as the line of Symmetry. When two or more parts are identical after a flip, slide or turn, the simplest type of Symmetry is "Reflection" (or "Mirror") Symmetry, as shown in this picture of my dog Flame. There is also Rotational Symmetry and Point Symmetry. The Symmetry of RD Sharma book deals with the lines of Symmetry, lines of Symmetry of geometrical objects such as rhombus, rectangle, triangle and a line segment, lines of Symmetry of some regular polygons such as equilateral triangle, square, regular pentagon, regular hexagon, lines of symmetry and reflection, rotational symmetry, angle of rotation and order of rotational Symmetry.