Computing the second fundamental form - can you spot the error?

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SUMMARY

The discussion focuses on computing the second fundamental form for a surface, specifically identifying errors in the calculations of IIx and IIy. The expected coefficients for IIuu, IIuv, and IIvv are 2, 0, and -2, respectively. The participants confirm that the calculations leading up to the da component in part (e) are accurate, but discrepancies arise in part (g). The issue lies in the missing computations for IIx and IIy, which should match the values obtained for IIz.

PREREQUISITES
  • Understanding of differential geometry concepts, specifically the second fundamental form.
  • Familiarity with surface parametrization and its derivatives.
  • Knowledge of tensor notation and its application in geometry.
  • Proficiency in mathematical computation techniques relevant to curvature analysis.
NEXT STEPS
  • Review the derivation of the second fundamental form in differential geometry.
  • Study the relationship between the first and second fundamental forms of surfaces.
  • Explore examples of surface parametrization to reinforce understanding of IIx and IIy calculations.
  • Investigate common errors in computing curvature-related forms in geometric analysis.
USEFUL FOR

Mathematicians, students of differential geometry, and researchers involved in surface analysis and curvature computations will benefit from this discussion.

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Homework Statement
Compute the second fundamental form of the surface.
Relevant Equations
Standard differential geometry formulas for the second fundamental form with Christoffel symbols.
Hi all. We are computing the second fundamental form corresponding to a surface.

The correct answer should give the coefficients 2, 0, and -2 for IIuu, IIuv, IIvv

We have only been able to compute IIz, and not IIx, IIy where we have functions instead of 2, 0 and -2.

We are 99% certain that everything up to the da component in part (e.) is correct. It is just in the last computations where an apparent errors are. Can you see where the error is in part g?
Screen Shot 2020-12-20 at 8.06.39 PM.png


Screen Shot 2020-12-20 at 8.06.44 PM.png

Screen Shot 2020-12-20 at 8.06.51 PM.png

Screen Shot 2020-12-20 at 8.06.55 PM.png


Screen Shot 2020-12-20 at 8.06.59 PM.png

Screen Shot 2020-12-20 at 8.07.03 PM.png


In part g, the II's corresponding to x and y should be the same as z. It seems like something is missing, perhaps. The second fundamental form were calculated using the following formula.
Screen Shot 2020-12-20 at 8.22.34 PM.png


Thank you!
 
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