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Lesson Plan #39 Class: Geometry Topic: Sum of the measures of the interior angles of a polygon Date: Friday December 9th, 2016 Aim: What is the sum of the measures of the interior angles of a polygon? Objectives: 1) Students will be able find the sum of the measures of the interior angles of a triangle. 2) Students will be able to find the sum of the measures of the exterior angles of a triangle. HW #39: Page 104 #’s 1-6, 8, 9, 10, 11 Do Now: Procedure: Write the Aim and Do Now Get students working! Take attendance Give Back HW Collect HW Notice each of the interior angles of the polygons at right measures less than 180o. These are known as convex polygons. If the polygon has at least one angle measuring more than 180o, it is called a concave polygon. Question:What do we call a polygon whose sides are all the same length and whose angles are all the same measure? Online Interactive Activity: Let’s see regular polygons in action. Let’s go to http://www.mathopenref.com/polygonregular.html We proved that the sum of the measures of the angles of a triangle is 180o and the sum of the measures of the angles of a quadrilateral is 360o. Let’s see how we can find the sum of the angles of a pentagon, then try to generalize a formula for the sum of the interior angles of a polygon of n sides. Examine the pentagon below. To help you discover the formula, see how many non-overlapping triangles you can create, then use this to come up with a sum of the angles of a pentagon. Try it for a six sided figure (hexagon). What is the formula for the sum of the interior angles of a polygon with n sides? Proof: http://www.qc.edu.hk/math/Junior%20Secondary/interior%20angle.htm Online Interactive Activity: Let’s check out the sum of the interior angles of a polygon in action. Let’s go to http://www.mathopenref.com/polygoninteriorangles.html Online Interactive Activity: Let’s check out the sum of the exterior angles of a polygon, taking one exterior angle at each vertex.http://www.qc.edu.hk/math/Junior%20Secondary/interior%20angle.htm http://www.mathopenref.com/polygonexteriorangles.html What is the formula for the sum of the exterior angles of any polygon of n sides, taking one exterior angle at each vertex? Sample Test Questions: 1) 2) What is the sum of the interior angles of a regular dodecagon (12-sided polygon)? 3) Each of the interior angles of a regular polygon is 156°. How many sides does the polygon have? 4) 5) 6) 7) 8) 9) 10) 11) 12) Assignment: Complete the exercises below