We used geogebra to examine the sum of the three angles of various triangles. We were able to see that the sum of these 3 angles is always 180 degrees. We completed our notes on 4.2.
Use the link for more examples.
http://www.khanacademy.org/math/geometry/parallel-and-perpendicular-lines/triang_prop_tut/v/triangle-angle-example-1
http://www.brightstorm.com/math/geometry/triangles/triangle-angle-sum/
Homework: WS 4.2