Use your handout with these directions to discover the formula for finding the sum of the interior angles of any polygon.

1. Complete the table on your handout up to a polygon with 8 sides. As you complete each row, look for patterns in order to predict the sum of the next shape.[br][br]2. Once you complete the octagon, make a prediction for the measurements of a dodecagon. Use the slider to check your answer. Were you correct?[br][br]3. If you were asked to calculate the sum of the interior angles of any polygon, you should be able to do it without using this page. Come up with a formula that will work for n sides. (Hint: Click on the "Show triangles" box for a clue)[br][br]4. Use your formula to predict the sum of the angles of a 20-gon and a 30-gon. Use the slider to check your prediction. If you were incorrect, adjust your formula to make it work.