Shape 

Copyright David & Cynthia Thomas, 2009

 

Necessary Conditions--Directed Activity: Angle Sums

                                                                                            

Focus

Investigate triangle angle sums

Technologies

·        Paper folding

References

·        Euclid of Alexandria

http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Euclid.html

Background

Figure 1.2 demonstrates the use of paper folding to investigate the angle sum of a triangle.  Starting with 3 different triangles, follow the indicated procedures.  Draw each triangle using a straightedge and cut it out carefully.

        

Figure 1.2: Angle Sums 

Tasks

1.      Investigate the relationship between the angles of all three triangles.  Summarize your findings in the form of a conjecture.

2.      Justify your conclusion.