Writing Parametric Equations from Cartesian Equations

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Discussion Overview

The discussion revolves around the methods for converting Cartesian equations into parametric equations. Participants explore the general approaches, complexities involved, and the usefulness of such parameterizations in various contexts.

Discussion Character

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

Main Points Raised

  • Some participants propose that for simple functions like y=f(x), one can use x=t and y=f(t) to create parametric equations.
  • Others argue that for more complex relationships, such as those defined by f(x,y)=0, the parameterization may not be straightforward, suggesting a form like x=g(t), y=h(t) where f(t)=f(g(t),h(t)).
  • One participant questions whether it is always possible to write parametric equations for any Cartesian equation in x and y, indicating uncertainty about the universality of this method.
  • Another participant notes that while it is possible to parameterize a function, the usefulness of such a parameterization can vary significantly depending on the context and intended application.
  • There is a suggestion that parameterization often begins with curves, where the parameter can be thought of as time, tracing out a trajectory.
  • Participants mention the difficulty in finding standard treatments or methods for parameterization, indicating a lack of consensus on a singular approach.
  • Links to external resources are provided for further exploration of parametric equations and their applications, but the relevance of these resources may depend on the specific context of the problem.

Areas of Agreement / Disagreement

Participants express differing views on the existence of a general method for parameterizing Cartesian equations, with some suggesting that multiple approaches are valid and others questioning the feasibility of parameterization in all cases. The discussion remains unresolved regarding the best practices for parameterization.

Contextual Notes

Participants highlight that the effectiveness of parameterization may depend on the type of function and the specific application, suggesting that there are limitations based on context and definitions.

Big-Daddy
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What is the general method for writing Cartesian equations as parametric equations?

For something as simple as y=f(x) we can write x=t and y=f(t) with the same function, but what about something more complicated, generally f(x,y)=0 - how can we make 2 parametric equations to represent a case where, for instance, both x and y have indices (neither 0 nor 1) in the Cartesian equation?
 
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Big-Daddy said:
What is the general method for writing Cartesian equations as parametric equations?
I don't think there is one. There are lots of ways to parameterise a relation.

For something as simple as y=f(x) we can write x=t and y=f(t) with the same function, but what about something more complicated, generally f(x,y)=0 - how can we make 2 parametric equations to represent a case where, for instance, both x and y have indices (neither 0 nor 1) in the Cartesian equation?

put: x=g(t), y=h(t) then f(t)=f(g(t),h(t)) is the parameterization.

The details depend on the type of function and what you need the parameterization for.
 
Ok, firstly, is it always possible to write a couple of parametric equations x(t), y(t) for any Cartesian equation in x and y?

Could you provide some links on how to convert from Cartesian to parametric equations?
 
You can always parameterize a function but you cannot always do so usefully.
i.e. say that z=f(x,y) represents the height of a terrain above a reference level ... what would be a useful parameterisation?

Depends on what you want to do with it right?

Usually you start out by parameterizing curves.
You can think of the parameter as a time value and the parameterization is the way the position coordinate changes with time. The resulting equation traces out a trajectory.

Treatments are a bit tricky to find since there are no standard ways to go about it.

Paul's notes deal with parametric equations (1st link) and an application to line integrals (2nd link).
http://tutorial.math.lamar.edu/Classes/CalcII/ParametricEqn.aspx
http://tutorial.math.lamar.edu/Classes/CalcIII/LineIntegralsPtI.aspx

The arc-length parameterization in some detail:
http://www.math.hmc.edu/math142-01/mellon/Differential_Geometry/Geometry_of_curves/Parametric_Curves_and_arc.html
 
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