From: Gail (for Teacher2Teacher Service)
Date: May 08, 1999 at 19:31:27
Subject: Re: Triangles

I second Roya's idea, with one variation. I have my students place a large dot just inside the 
corner of each vertex, and then TEAR the corners off the triangles. That way, when they go where 
the vertices, they are combining the appropriate angles without much confusion.

I would 
also suggest that you begin with one type of triangle, and then have students decide if they 
think other triangles' angles would behave in the same way. They could then explore that idea 
by tearing the corners of a variety of triangles (isosceles, scalene, right and equilateral) 
and piecing them together.

An extension to this activity is to have students decide if the 
sums of other figures with more than three sides have sums greater, or less than, 180. They can 
even make predictions, and then find out by doing the same sort of things with the corners. They 
might even investigate a variety of different quadrilaterals to see if the sum remains the 
same for all figures with four sides.

 -Gail, for the Teacher2Teacher service

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