Geometry for Teachers

Math 445, Winter 1999

University of Washington

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Week 7 Syllabus

Reading

  • Review Sved, Ogilvy and Bix on orthogonal circles, the models, and the hyperbolic plane. Also review Bix and An Eye for Similarity Transformations on dilations.

 445 Monday, February 15

HOLIDAY

 445 Wednesday, February 17

Introduction to Projective Geometry. Definition of parallel and central projection. Example of projection of two intersecting roads leads to method for finding projection of midpoint. (This is harmonic division in disguise.)

 487 Computer Lab 7, Wednesday, February 17

A first lab exercise was to draw the projection of the intersecting roads to see that the image of the midpoint of AB is unchanged if the images of A, B and the point at infinity on line AB are fixed.

The rest of the lab was devoted to exploring spherical geometry with Sketchpad using stereographic projection to map the sphere to the plane. Sketchpad scripts for this, along with sketches explaining this, are on the server.

 445 Friday, February 19

Desargues Theorem. Class exercise on converse of Desargues by beginning with points P, Q, R on a line (the fold of a manila folder) and drawing two triangles P1 Q1 R1 and P2 A2 R2 perspective from the line (e.g., lines P1Q1 and P2 Q2 pass through R, ...). In this case the lines P1P2, Q1 Q2 and R1 R2 are concurrent.

Assignment 7 Part A is due on Wednesday, 2/26

Assignment 7 Parts B and C are due on Friday, 2/28