The projective and kinematic geometry of closed polygons (1914)
Hebbert, Clarence Mark · leaf 50
focal parabolas, five fixed lines, andfive infinite sets of circles tangent to the five fixed lines andconcurrent at the common focus of the parabolas. These seem toexplain the apparent (though only apparent) dualism of the theoremsrelating to quadrilaterals having an infinite number of… … MECHANISM TO ILLUSTRATE THEOREM V. The slotted pieces AE, BD, DC, CA, turn about the fixedpoints F, E, K, 0, respectively. The pins A, B, C, D, are thefour vertices of a variable square and move on the circleswith centers Cj, Cg, Gg, O4. The center of the variable squaredescribes the circle with…
