Using Ti-89 to solve for Three dimensional Principle Stresss

[Northbysouth]

I've got a TI-89 Titanium

I've taking a class in Mechanical Design and my professor informs me that we need to be able to solve the equation (equation 3-15) shown in the attachment. I've been trying to find a way to program it into my calculator, but haven't had any real success.

The purpose of the program is to solve for sigma

I tried writing a program with ProgramEditor. I followed the outline given at:

https://epsstore.ti.com/OA_HTML/csksxvm.jsp?nSetId=91276

But when I attempt to use the equation in HOME it asks me for sigma, which is what I want to solve for.

Any suggestions on what I could do?

Help is always appreciated.

 

[Greg Bernhardt]

I'm sorry you are not finding help at the moment. Is there any additional information you can share with us?