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If two lines a and k pass through a single point Q, then the polar q of Q joins the poles A and K of the lines a and k, respectively. The concepts of a pole and its polar line were advanced in projective geometry. For instance, the polar line can be viewed as the set of projective harmonic conjugates of a given point, the pole, with respect to ...
In Euclidean space, the dual of a polyhedron is often defined in terms of polar reciprocation about a sphere. Here, each vertex (pole) is associated with a face plane (polar plane or just polar) so that the ray from the center to the vertex is perpendicular to the plane, and the product of the distances from the center to each is equal to the square of the radius.
Polar reciprocation, a concept in geometry also known as polarity Trilinear polarity , a concept in geometry of the triangle Polarity of a literal , in mathematical logic
In the complex number approach, where reciprocation is the apparent operation, this procedure leads to the complex projective line, often called the Riemann sphere. It was subspaces and subgroups of this space and group of mappings that were applied to produce early models of hyperbolic geometry by Beltrami , Cayley , and Klein .
The dual can be visualized as a locus in the plane in the form of the polar reciprocal. This is defined with reference to a fixed conic Q as the locus of the poles of the tangent lines of the curve C. [2] The conic Q is nearly always taken to be a circle, so the polar reciprocal is the inverse of the pedal of C.
Reciprocation may refer to: Reciprocating motion , a type of oscillatory motion, as in the action of a reciprocating saw Reciprocation (geometry) , an operation with circles that involves transforming each point in plane into its polar line and each line in the plane into its pole
The dual of a convex polyhedron can be obtained by the process of polar reciprocation. [34] Dual polyhedra exist in pairs, and the dual of a dual is just the original polyhedron again. Some polyhedra are self-dual, meaning that the dual of the polyhedron is congruent to the original polyhedron. [35]
This correspondence can also be seen as an example of polar reciprocation, a general method for corresponding points with lines and vice versa given a fixed circle. Although they do not touch the circle, the four vertices of the kite are reciprocal in this sense to the four sides of the isosceles trapezoid. [ 30 ]