I was in the process of looking at some lifting structures and have managed to produce a very strange error.

I have derived an angle which I then use in a later Sin function. If I simply give an answer the result it correct but if I define a symbol to the function and check the value of the symbol the answer is hugely incorrect.

File can be found here:
http://files.engineering.com/getfile.aspx?folder=5166b729-a993-4a6f-8c50-243a4cca72c8&file=Sin_Error_-_Copy.sm

I have reproduced the error again at the bottom of the page with different values.

Wondered whether anyone can reproduce this error or offer any insight?

Try this. Change Optimization to Numeric.

First Select all SMath items.

From Calculation Menu -> Optimization -> Numeric.

I'm a civil engineer and perform a lot of structural calculations using SMath. Calculations with units helps to avoid errors, kips vs. lbs, inch vs. feet, etc. I have often encountered similar strange results and 99% of the time Optimization->Numeric solves the problem. I've found its important to display the results of each calculation just to see if it makes sense. I notice you're doing the same thing. Good engineering habit.

I wish default Optimization was Numeric. Don't know what Symbolic is used for.