Is There Only One Intersection Point on the y=2^2 Curve for the Tangent Line at P(x0, x0^2)?

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Discussion Overview

The discussion revolves around the uniqueness of intersection points between a tangent line at a point P(x0, x0^2) on the curve y=x^2 and the curve itself. Participants explore the implications of tangents to parabolas and the nature of their intersections.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to prove that the only intersection point of the tangent line at P(x0, x0^2) with the curve y=x^2 is P itself.
  • Another participant suggests that proving the uniqueness of the tangent line at a specific point is trivial, as all tangents at that point share the same slope and pass through it.
  • A different participant questions whether the slope is the same at two points due to symmetry, indicating a potential misunderstanding of the tangent concept.
  • Another participant notes that a line can intersect a parabola at most twice, with tangents counting as double roots in the context of quadratic equations.

Areas of Agreement / Disagreement

Participants express differing views on the nature of tangents and their intersections with parabolas. There is no consensus on the uniqueness of intersection points, and the discussion remains unresolved.

Contextual Notes

Participants reference the properties of quadratic equations and tangents, but there are unresolved assumptions regarding the definitions and implications of these properties.

danne89
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Please help me prove that it doesn't exist any other intersect point than P(x0, x0^2) on the y=2^2 curve, for the tangent line in the very same point.

My work:
y=x^2
l(x)=f¨(x0)(x-x0)+x0^2
= 2x0(x-x0)+x0^2
= 2x0x-2x0^2 + x0^2
= 2x0x - x0^2
 
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You mean to prove the uniqueness of the tangent to a parabola in one certain (albeit arbitrary) point...?That's trivial.The slope is the same (unique) and they all pass through the same point (namely,the tangence point),therefore,all tangents coincide.

Unless,you meant something else...

Daniel.
 
Hey, isn't the slope the same in two points (symmetry over the y-axis.) ?

Edit: Ohh, my no. It's mirrored...
 
Last edited:
Yes,it picks up the minus (due to the cosine,which is negative,once you enter [itex](\pi/2,\pi)[/itex])...

Daniel.
 
in general a line can only intersect a parabola twice at most and tangent intersections count as 2. done.

i.e. when you substiotute the parametrization for the loine into the poarabola equation you get a quadratic which can have only 2 roots, and tangents are exactly those points where the root is a double root.
 

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