Hexahedron Shapes Polygons Symmetry Nets Tetrahedron Exterior Angles

Hexahedron Shapes Polygons, Symmetry, Nets Tetrahedron

Exterior Angles • These are the angles on the outside of the shape • They add up to 360° There are 5 sides to a pentagon Therefore each angle is 72°

Interior Angles • The angles inside a polygon are called internal angles • They always make a straight line with the exterior angle • Interior angle + Exterior angle = 180° If the exterior angles are 72° We can work out the internal angles 180 – 72 = 108°

Tessellations • This is a pattern made by repeating the same shape over and over again • E. g.

Sum of Interior Angles 1. 2. 3. 4. 5. Draw your polygon Join one vertex (corner) to all the others Count the number of triangles Multiply this by 180° Divide this by the number of sides How many triangles are there? 6 6 x 180° = 1, 080° How many sides does this shape have? 8 1080/8 = 135° for each interior angle

Lines of Symmetry • A line of symmetry divides a shape into 2 equal parts • It can also be called an axis • How many lines of symmetry does this shape have? 4

Rotational Symmetry • A shape has rotational symmetry if it fits on top of itself more than once as it makes a complete turn • The order of rotational symmetry is this number • What is the order of rotational symmetry for this shape? 8

Plane of Symmetry • This divides a solid (3 d) into two equal parts

Net • A net is a pattern of shapes that can be folded into a hollow solid • These three patterns make the same shape. What is it? A Cube

Nets • Most nets have flaps to help you stick the shape together • The flaps only need to be on half the sides • How many sides does this shape have? • 4 This is a tetrahedron

Questions • What solids can be made with these nets?

Answers • Cylinder • Pyramid • Tetrahedron