How Can I Find Tangents on a Surface Passing Through an External Point?

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Discussion Overview

The discussion revolves around finding the equations of tangents on a surface that pass through an external point located outside the surface. The problem is approached from both 2D and 3D perspectives, with considerations for the nature of the surface and the tangents involved.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • AtulSharma presents a problem of finding tangents on a surface from an external point.
  • Some participants express uncertainty about the problem's seriousness and seek clarification on the need for an answer.
  • One participant suggests differentiating the surface implicitly to find the slope of the tangent line at any point, proposing a relationship between the tangent slope and the coordinates of the external point.
  • Another participant agrees with the proposed method but emphasizes the need for further input from others.
  • A question is raised regarding whether the problem is in 2D or 3D, with implications for the number of tangents that can be found.
  • It is clarified that the problem is indeed 3D, with a focus on finding some tangents that pass through the external point rather than all possible tangents.

Areas of Agreement / Disagreement

Participants express differing levels of confidence in their reasoning, and there is no consensus on the best approach to solve the problem. The distinction between 2D and 3D interpretations also introduces potential disagreement regarding the nature of the solution.

Contextual Notes

Participants note the complexity of the surface may affect the solution, particularly if it has both concave and convex components. There is also uncertainty about the completeness of the proposed methods and the assumptions involved.

Who May Find This Useful

This discussion may be of interest to those studying calculus, differential geometry, or anyone dealing with geometric problems involving tangents and external points.

AtulSharma
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Finding Tangents... Interesting !

Hello,

I have an interesting problem for you.

I have a surface & an external point which is outside the surface.

I need to find the equation of all the tangents on this surface which pass through the external point.

Regards,
AtulSharma
 
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AtulSharma said:
Hello,

I have an interesting problem for you.

I have a surface & an external point which is outside the surface.

I need to find the equation of all the tangents on this surface which pass through the external point.

Regards,
AtulSharma
Are you just trying to test us, or you really need an answer to this question?
 
I myself need an answer to the problem.
 
well, i am not sure whether my reasoning will be fine, because you have this surface, so if it were a curve it would most likely go like this.
You first find the derivative of that function, most likely you will have to differentiate it implicitly, so this way you will manage to find the slope of the tangent line at any point on that surface, curve. So now you have this external point call it (x_1,y_1), so now the slope of the tangent will be

\frac{y-y_1}{x-x_1}=m, but now you also have the slope of the tangent line at any point dy/dx so

\frac{dy}{dx}=\frac{y-y_1}{x-x_1}, so you will manage to find a relation between x, and \ y but you also have one relation given by the eq of the curve, so i think now you have to look for a solution, when this line only touches that curve. I am not sure whether my reasoning is okay, but wait for other replies as well!
 
Well, I think its a good way to try. Let's see other replies also.

Thanks for this solution.
 
Is this a 2D or 3D problem. If it's a 3D problem, are you looking for all the tangent planes that include the outside point, or only tangent lines that go through the point (in this case you end up with a cone)? If it's a 2D problem then you just end up with 2 lines. This is assuming the surface isn't complex, such as one that has both concave and covex components.
 
This is a 3D problem. I need to find some (not all) of the tangents passing through the external point.
 

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