Course:Harris, Fall 07: Diary Week 2

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(short week)


  • collected Polygon Exercises
  • class finished up last week's Tessellations Exploration (~20 mintues), turned it in
  • took first look at Kali (~20 minutes), considering what different types of symmetry were being created
  • started working on Symmetry of Stars Exploration, but didn't finish


  • spent most of the class (~30 min) delving into #3 of last week's Exercises:
    • why triangle angle-sum is 180 (opposite interior angles)
    • why quadrilateral angle-sum is 360 (two interior triangles)
      • why one has to be careful with diagonals for non-convex quadrilaterals
    • why, in a quadrilateral, opposite angles being congruent implies opposites are parallel
      • need to get to opposite interior angles
      • that means need to show adjacent angles add to 180
      • how to get to that by using quadrilateral angle-sum is 360
  • class finished up Symmetry of Stars Exploration
  • just began to discuss Rotational and Reflectional Symmetries in Escher Exploration