Monday, March 30, 2015

Geoboard app + polygons

Usually when it is time to start a new section, I give the students a reading assignment before covering the material but this time I am approaching polygons and their interior measures a bit differently.  I am having them do the exploration before reading the section.  The exercise has them draw various polygons beginning with a triangle, then a quadrilateral, pentagon, etc.

 As they  create the polygon on geoboard, they subdivide the shape into triangles.  They use the triangles to calculate the total angle measure and the measure of each angle. 

This gives them a chance to create and discover the answer.  I've used this exercise in the past but had them actually draw the shapes but this time I decided to save paper and have them do it on the geoboard app.  The first part of the exercise has them create certain polygons and subdivide the shape into smaller triangles to find the formula 180(n-2). The second part requires that they find a point inside the shape and create lines from the point to the vertex to find smaller triangles.  This leads them to the 180(n-2) via 180n - 360. 
This exercise is allowing them to build or strengthen their foundational knowledge before they read the section tomorrow.  I am hoping this will give them a better understanding of the material since most of my students are ELL. 
This activity kept my students engaged the whole period and it was easier because no paper was used, no lost rubber bands or broken boards.  I am going to use this activity again.