## Thursday, 21 September 2017

### 21 Sep 2017: What we did today...

Focus of Revision on POLYONS
• Key ideas
• Naming polygons (up to 10 sides)
• Revisited the formula and how to derive them, as well as the relationship:
• Sum of interior angles of a polygon = (n - 2) x 180º (using a pentagon to help us visualise)
• Sum of exterior angles of a polygon is always 360º (using an equilateral triangle and square to help us visualise)
• Interior angle + Exterior angle = 180º
• When one increases, the other decreases
• How to deal with polygons of unusual shapes
• Discussion (1) with the following papers:
• HIHS 2017 S2 Mid-Year Exam Paper 2 Q9
• CGS 2015 S2 Mid-Year Exam Section B Q3
• FMS 2015 S1 EOY Exam Paper 1 Q11
• NYGHS 2015 S1 EOY Exam Paper 2 Q5
• Discussion (2) with handout WJEC CBAC GCSE papers
Solution presented by Corwin

• Note that, when the context is defined here, that we know that n must be an integer (since it represents the number of sides of a polygon), we may leave out defining n is an integer. However, when without context, we should define n when constructing the inequality. (with inputs with Ethan)

Next week (T4W3), we will move into the following topics:
• Mensuration (Perimeter, Area, Volume), which involves simple algebra
• Linear Graphs, Sketching
• Algebra
• Construction will be kept to the last week of the revision

Do attempt the other schools' exam papers to prepare for the upcoming topics.