Course Guide - USAID Teacher Education Project

each group has a second polygon with the number of sides double that of the first.Later you will ask if the angle sum doubles when you double the number of sides. Ifnot, why not?)Have student groups draw various polygons with a given number of sides, dividethem into triangles with diagonals, and calculate the angle sum.Have students report out to create a chart similar to that above. Ask how doubling thenumber of sides related to the angle sum. Ask what patterns they notice. As theyexpress their thoughts, ask what the pattern implies about finding the angle sum for apolygon with any number of sides.Once they have discussed this in informal terms (but before they share a formula), askstudents to write a formula they could use to find the angle sum of any polygon. Thereare several ways to express this, such as (n-2)*180, n*180-360, etc. If differentformulas emerge, use these formulas as an opportunity to show how they areequivalent expressions.e) Return to the homework assignment about arranging pattern blocks around a pointto form a 360° angle. Did some students use only the paper cutouts? Did others usethe virtual pattern blocks from the Internet? What were their discoveries? How didusing a recording sheet help organize their thinking and encourage predictions? Whatwere their findings? Were there any surprises?5) Assignments and Resources:a) Have students bring crayons or felt-tip markers to the next class.b) Have students review the following websites that will review concepts taught inthis lesson:1) Triangle dissection of polygonsReview of dissecting polygons into triangles: http://tinyurl.com/AlgLab-Angle-Sum2) Angle sumsUsing patterns to discover the angle sum formula (video):http://tinyurl.com/Angle-Sum-Patterns3) Developing the angle sum formula: http://tinyurl.com/Angle-Sum-Formula1