Looking for tips on sketching of 3-d graphs?

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Discussion Overview

The discussion revolves around techniques for accurately sketching 3-dimensional graphs, particularly in the context of multivariable calculus, focusing on double integrals and the representation of various shapes such as cylinders.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses difficulty in sketching 3D graphs accurately, even for simple shapes like cylinders, and seeks tips for improvement.
  • Another participant suggests using "level curves" and drawing cross sections in the coordinate planes to aid in visualization.
  • A participant describes their method of drawing the coordinate axes, indicating a vertical axis for Z, a horizontal axis for Y, and a diagonal representation for X, and seeks clarification on proper techniques.
  • A later reply reiterates the suggestion of using cross sections and introduces the "trace method," which involves substituting different values for variables to create 2D graphs in planes perpendicular to the substituted points.

Areas of Agreement / Disagreement

Participants generally agree on the utility of drawing level curves and cross sections as helpful techniques for sketching 3D graphs, though there is no consensus on the best method for drawing coordinate axes.

Contextual Notes

Some participants mention specific methods without detailing the underlying assumptions or limitations of those methods, and there is no resolution on the best practices for sketching coordinate axes.

maximf
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basically I'm in the last 2 chapters of multi variable calculus (right now in double integrals) and i know how important it is in some exercises to sketch the 3-d graphs accuratley. However all the 3-d graphs that I'm trying to sketch are very off... even a simple shape like a cylinder looks bad.

anyway are there any tips for manual sketching that might help me graph the functions little more accuratley?
 
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Drawing "level curves" should help. One thing I like to do is draw cross sections in the coordinate planes: if x= 0, what is the graph in the yz-plane? If y= 0, what is the graph in the xz-plane? If z= 0, what is the graph in the xy-plane? The imagine those graphs place on the coordinate axes.
 
how do you properly draw the coordinate axes? what i do is sketch one vertical that will be Z and one horizontal that will be Y. and the X axis i draw diagonally through the squares (i use math paper obviously...)
 
HallsofIvy said:
Drawing "level curves" should help. One thing I like to do is draw cross sections in the coordinate planes: if x= 0, what is the graph in the yz-plane? If y= 0, what is the graph in the xz-plane? If z= 0, what is the graph in the xy-plane? The imagine those graphs place on the coordinate axes.

Yes. This is probably the best way to do it. Just substitute different values for the individual variables in the equation. This will give you the 2d graph created with the remaining variables on the plane perpendicular to the point at which you have substituted. Just do this a few times for all of the different variables and you will be able to shade in a complete 3d graph.

My teachers call it the trace method.
 

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