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 [color=#980000][b]8 sides[/b][/color]. 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 [b][color=#980000]prediction[/color][/b] for the measurements of a [color=#980000][b]dodecagon[/b][/color]. 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 [b][color=#980000]n[/color][/b] 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 [color=#980000][b]20-gon[/b][/color] and a [b][color=#980000]30-gon[/color][/b]. Use the slider to check your prediction. If you were incorrect, adjust your formula to make it work.[br][br]5. What is the sum of the angles of a [b][color=#980000]40-gon[/color][/b], [b][color=#980000]45-gon[/color][/b],and a [b][color=#980000]50-gon[/color][/b]. Use the slider to check your prediction. If you were incorrect, adjust your formula to make it work.