Triangles and Polygons Powerpoint

A triple purpose PowerPoint, first it shows the naming of triangles, next the activity of showing that the triangle angle sum is 180°. Thirdly it uses triangles to calculate the angle totals for polygons, introduces the formula, and lastly considers the application to more complex shapes with areas where errors can occur, so encouraging formula memorization and use.
I use this PowerPoint in parts to save on board work, for several different classes. No worksheets are included since textbooks usually include enough practice exercises.