Sketch of curves defined by parameters

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Discussion Overview

The discussion revolves around the sketching of a curve defined by the parametric equations r(t) = (sin(t), cos(t)) for 0 ≤ t ≤ 2π. Participants explore the interpretation of these equations, the nature of the curve, and methods for graphing it, including the transition between polar and Cartesian coordinates.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant questions whether sketching the curve involves simply drawing the graphs of sin(t) and cos(t).
  • Another participant suggests that the equations represent a polar coordinate system, where sin(t) and cos(t) correspond to the x and y coordinates of a vector, indicating that it is a single graph rather than two separate ones.
  • A different participant points out that the relationship x² + y² = 1 indicates the curve is a circle, but clarifies that t should be considered as the angle from the positive y-axis, not the x-axis.
  • One participant proposes that converting the polar coordinates to Cartesian coordinates might help in graphing the curve, providing the transformation equations for clarity.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the parameter t and its relation to the axes, as well as the method for graphing the curve. There is no consensus on the best approach to sketch the curve or the implications of the parameterization.

Contextual Notes

Participants note potential confusion regarding the interpretation of the parameter t and its geometric implications, as well as the transition between coordinate systems, which may require additional clarification.

smoothman
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silly question. didnt know where it was meant to go so i just put it here as safest option:)

suppose a curve C is defined by, r(t) = (sint, cost) with 0 \leq t \leq 2\pi

if a sketch of C was required then would you simply just draw the graphs for sint and cost?
 
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Based on the equation, it's appears that polar coordinates are being used, where r is the length of the vector, and t is the angle of the vector from the x axis. Sin(t) and Cos(t) are the x and y coordinates of the polar vector. This is a single graph, not two.
 
Last edited:
If r(t)=(sint, cost) then x component is sint, y component is cost
which means
x^2+y^2=1 as you know it is a circle
but t is not an angle of the vector from x axis( it is valid for (cost,sint))
For our curve if we take t=0 , we obtain the pt (0,1) which is on the y axis
Therefore in our case t is angle from +y -axis

didnt know where it was meant to go so i just put it here as safest option:)
Not sure but this type of questions are generally discussed at homework section
 
Just thought that a good idea in order to graph the curve C which you have, as Jeff said, written in polar coords. ,if you do not see of-hand how to graph it, would be to switch back (if/where possible) between polars, to Cartesian coordinates, which are the coordinates I think most people are familiar with in terms of doing graphs.

The coordinate change is given by:

x=rcost
y=rsint

and the inverse maps.
 

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