Friday, January 25, 2013

A Great Way to Help Students Discover the Sum of the Interior Angles in Polygons!

Hello again, I thought I would share another great discovery lesson that worked really well! I completed this lesson Wednesday with my 7th grade students and it was very successful. In order to get my students to understand the concept of finding the missing angles of various polygons, I started with a short activity dealing with triangles. It is not a new idea, and I do not take credit for it, but it was a great starting point for this lesson. This lesson would be very easy for you to recreate on your own, however if you want the pre-made UBD Lesson Plan and all necessary templates, you can look for it at my TpT store at:

Once the students have finished discovering that ALL triangles have three angles that add up to 180 degrees, they then investigate how many triangles are in each polygon. I created a quadrilateral, pentagon, hexagon, haxagon, heptagon, and octagon for them to investigate. They should arrive at teh conclusion that there is a pattern. The number of sides a polygon has minus 2 equals the number of triangles. They know that a triangle equals 180 degrees, so to figure out the sum of the interior angles, you just multiply the number of triangles by 180 degrees.
Students started with a random triangle that they cut out. They
labled and highlighted each angle.



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