Talk:Introduction to Elasticity/Principal stresses

I was just trying to apply this to the matrix [2 1 1 / 1 2 1 / 1 1 2 ] and the cos^-1 blew up on me. I found 1026/54 for my invariants. If this is supposed to be 1/cos, please clarify, because cos^-1 is usually understood as arccos. DragnBludthrsty (discuss • contribs) 17:24, 8 October 2017 (UTC)

In the formulas for principal stresses in three dimensions it seems that the formulas for the second and third principal stresses have been switched. Am I correct? I base this on a check I did with results from a FEM analysis.

// 15.09.15 AZinovyev: Yes, you are right! I checked on Visage outputs, Here S2<S3. Should me switched

3D principal stress
Where can I found a source (book, article, hint) for calculation of the principal stresses in three dimensions?

Improved navigation
It will be helpful if navigation to a learning resource that can place this in context can be improved. I assume, based on the "related content" entry, that this is part of a sequence or course on elasticity. It will be helpful if some navigation aid, perhaps a navigation bar at the bottom, can be added to help put this more clearly in context. Thanks! --Lbeaumont (discuss • contribs) 12:05, 2 December 2017 (UTC)