Geometry
2D Shapes
2D (flat) shapes can be drawn on paper. A square has 4 equal sides and 4 corners, a rectangle has 4 sides (two long, two short) and 4 corners, a triangle has 3 sides and 3 corners, and a circle is round with no corners.
The straight edges are sides and the points where they meet are corners (vertices).
- Square and rectangle: 4 sides, 4 corners.
- Triangle: 3 sides, 3 corners. Circle: round, no corners.
3D Shapes: Faces, Edges, Vertices
3D (solid) shapes take up space. A cube (like a dice) has 6 faces, 12 edges and 8 vertices. A cuboid (like a brick) also has 6 faces, 12 edges and 8 vertices. A sphere is like a ball, a cylinder like a tin, and a cone like an ice-cream cone.
A face is a flat surface, an edge is where two faces meet, and a vertex is a corner.
- Cube and cuboid: 6 faces, 12 edges, 8 vertices.
- Face = flat surface; edge = where faces meet; vertex = corner.
Lines & Symmetry
Lines can be straight, curved or slanting. The edge of a ruler is a straight line; the letter S is made of curves.
A shape has line symmetry if a line can divide it into two equal halves that match exactly, like a mirror. That line is called a line of symmetry. A square has 4 lines of symmetry.
- Lines can be straight, curved or slanting.
- A line of symmetry splits a shape into two matching halves.