Level Curves and Visualization of Surfaces

 

 

Example:  Draw several level curves for the graph of     f(x,y,z)  =  36x2 + y2+ 36z2 ˗ 36 = 0

 

Strategy:   

1.  First check for symmetry.  Note:  f(x,y,z)  =  f(˗x, ˗y, ˗z) 

     Result:             The graph of f(x,y,z) is symmetric about all three axes.

 

Next plot traces.

2.  Traces for     x = k = constant.     

So                  y2+ 36z2  =  36 ˗ 36k2     which are ellipses for |k| < 1.

 

3.  Traces for    y = k = constant.     

 

So                  36x2  + 36z2  =  36 ˗ k2     which are circles for |k| < 1.

4.  Traces for     z = k = constant.     

So                  36x2 +  y2  =  36 ˗ 36k2     which are ellipses for |k| < 1.



Result:  The graph is an ellipsoid centered at the origin with intercepts at

 

                    x  =  ± 1  ,  y  =  ± 6,  and  z  =  ± 1

 

See the figure below.

 

 

                                  

 

 

 

 




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