Ellipse in the projected square

[JuneTheSecond]

Visio ellipse is cool, because ellipse can be drawn when special 3 points are given.
I've drawn an ellipse in such a way.
Contents of attatched drawing
Page 1. Projection of Circle and Square
Page 2. Visio ellipse is cool,,,
Page 3. Center Projection from Horizontal Plane to Screen
Page 4. Cross Ratio
Page 5. Using Cross Ratio
Page 6. Calculating t to draw,,,
Page 7. Visio Projective Geometry