12.6 Volume and surface area of cones and spheres -- Key points -- Internet Challenge 12 -- 13 Geometric constructions -- Starter: Round and round in circles -- 13.1 Constructing triangles from given information -- 13.2 Constructions with line segments -- 13.3 Bearings -- Key points -- Internet Challenge 13 -- 14 Transformation and similarity -- Starter: Monkey business -- 14.1 Reflections -- 14.2 Rotations -- 14.3 Combining transformations -- 14.4 Enlargements -- 14.5 Similar shapes and solids -- Key points -- Internet Challenge 14 -- 15 Pythagoras' theorem -- Starter: Finding squares and square roots on your calculator -- 15.1 Introducing Pythagoras' theorem -- 15.2 Using Pythagoras' theorem to find a hypotenuse -- 15.3 Using Pythagoras' theorem to find one of the shorter sides -- 15.4 Pythagoras' theorem in three dimensions -- 15.5 Pythagoras' theorem on a coordinate grid -- Key points -- Internet Challenge 15 -- 16 Introducing trigonometry -- Starter: A triangular spiral -- 16.1 The sine ratio -- 16.2 The cosine ratio -- 16.3 The tangent ratio -- 16.4 Choosing the right trigonometrical function -- 16.5 Finding an unknown angle -- 16.6 Multi-stage problems -- 16.7 Angles of elevation and depression -- Key points -- Internet Challenge 16 -- 17 Circle theorems -- Starter: Circle vocabulary -- 17.1 Tangents, chords and circles -- 17.2 Angle properties inside a circle -- 17.3 Further circle theorems -- 19.4 Intersecting chords -- Key points -- Internet Challenge 17 -- 18 Sets -- Starter: Does it all add up? -- 18.1 Introducing set notation -- 18.2 Venn diagrams -- 18.3 Further Venn diagrams -- Key points -- Internet Challenge 18 -- 19 Working with data -- Starter: Lies, damned lies and statistics -- 19.1 Calculations with frequency tables -- 19.2 Solving problems involving the mean -- 19.3 Histograms -- 19.4 Cumulative frequency