Deriving the Polar of a Point on a Conic

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SUMMARY

The polar of a point P(p, q) with respect to a general conic defined by the equation ax² + 2hxy + by² + 2gx + 2fy + c = 0 is given by the equation apx + h(py + qx) + bgy + g(p + x) + f(q + y) + c = 0. This derivation is based on the concept that the polar represents the chord of contact of the tangents drawn from point P to the conic. If point P lies on the conic, the chord of contact becomes non-existent, as the tangents coincide at that point. Understanding the implicit derivative is crucial for deriving the tangent line from point P.

PREREQUISITES
  • Understanding of conic sections and their equations
  • Knowledge of polar coordinates and their geometric interpretations
  • Familiarity with implicit differentiation techniques
  • Basic concepts of tangents and chords in geometry
NEXT STEPS
  • Study the derivation of the tangent line from a point to a conic
  • Explore the properties of polar lines in conic sections
  • Learn about implicit differentiation in calculus
  • Investigate the geometric significance of the chord of contact
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Mathematicians, geometry enthusiasts, students studying conic sections, and anyone interested in advanced calculus and its applications in geometry.

Appleton
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If a general conic is

<br /> ax^2+2hxy+by^2+2gx+2fy+c=0<br />

I am told that, if P(p, q) is a point on this conic, then the polar of P(p, q) to this conic is

<br /> apx+h(py+qx)+bgy+g(p+x)+f(q+y)+c=0<br />

How is this derived?
 
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What is your definition of the polar of a point wrt the conic? What do you know about the polar if the point lies on the conic?
 
Thanks for your reply micromass. I realize I made a mistake. P(p,q) does not lie on the conic.

The polar is the chord of contact of the tangents from P.

If the point lies on the conic then the chord of contact would be non existent as P and the tangent points would all be coincident.

If we assume there are no constraints on P, what would be the derivation?
 
Do you know the equation of the tangent line from ##P##?
 
OK I think I'm with you now. Thanks for the prompt. I think the implicit derivative was my main stumbling block, amongst various other oversights.
 

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