Thursday,  September 25
Collect Project  Proposals  and   1 or 2 portfolio sample entries. 
  • ISOMETRIES: Rigid Motions in (or about) the plane.  Also called "Isometries"
  • Orientation preserving
  • Translations
  • Rotations
  • Orientation reversing
  • Reflections
  • Glide reflections

    • Classification of Isometries
    Video : Isometries
    The video introduced the four isometries we have discussed:
    reflections, rotations, translations, and glide reflections.

    It was shown that the product of two reflections is either a rotation (if the axes of the reflection intersect)  or a translation (if the axes of the reflection are parallel).



    Wingeometry demonstration for reflection- one and two reflections
    What about 3 reflections? 

    Every plane isometry is the product of at most three reflections.
    discuss basic idea:
    Reflection is related to "perpendicular bisector" of PP'
    With a triangle the 3 vertices ABC -> A'B'C' may be related to at most 3 lines of reflection.
    Two reflections = rotation or translation.
    Three reflections = reflection or glide reflection
    How to figure out what isometry you have.... match features.
     

    		Preserve
    Orientation    		 Reverse
    Orientation
    No Fixed points Translation Glide reflection
    Fixed Point(s) Rotation Reflection

     
  • Using Isometries to create variations of tilings
  • 180 degree Rotations 
  • Translations
    • Space: How do we understand objects in space?
    How can the Flatlander experience the sphere and space?

    Cross sections
    shadows
    fold downs- flattened figures
    analogue...  point... line.... polygon.... polyhedron......
    • Some Issues we'll consider in space:
    • Platonic (regular convex polyhedra) Solids
      • Why are there only 5?
        • Regular polygons around a vertex.
        • All vertices are "the same".
    • Symmetries (Isometries) in the plane compared to those in space- an introduction:
        • Translations
        • Rotations: Center point - central axis
        • Reflection :  across line - across plane
    • Symmetries of the cube:
        • Rotations
        • reflections
        • rotation- reflection
    • Isometries in space: products of reflections in space:
      • Rotations and translations
      • Applications to dance