Elicit non-trivial dialogue from students. Guide students to reflection and analysis of the experience. Encourage students to share their perceptions and beliefs. Summarize and review similarities and differences.

Analyze the ping pong ball experiment and need for rules.

Objective: To analyze the ping pong experience. Students will realize that the term "triangle" is relative to the system and that Euclidean geometry only works in two dimensional space. "Rules" are therefore relative: new situations demand new rules.

Activity: Teacher leads class discussion. What is a triangle? What is the range of the sum of the angles of a spherical triangle? How can "hunches" about this range be tested?

Assessment: Student recognition of the need for developing new rules and testing them.