Wow. Cant thank you enough for the redundant parentheses tip. What a relief.
You're welcome.
Earlier you wrote:
Yes the iterative calcs [...]. Although there is no direct circular ref, the irrational #'s, are in a way circular.
I'm not sure what your misunderstanding is. Perhaps a literal translation of PI() and trig functions like COS() as so-called "circular" functions in math.
In any case, there is no relationship between Iterative calculation mode and calculations with or that result in irrational numbers. They are not "in a way circular", as the term applies to Excel.
In Excel, "circular" refers to self-referencing formulas or a system of formulas that inter-reference each other.
Iterative calculation mode and the Max Iterations count affect only how many such circular iterations Excel will tolerate. In particular, Max Iterations does not affect the number of iterations in internal algorithms such as RATE, IRR and Goal Seek.
Bottom line: Unless you have purposeful (circular) self-references in formulas, it would behoove you not to set Iterative calculation mode.
And if you have purposeful (circular) self-references in formula, it would behoove you to reconsider your design. In my experience, Iterative calculation mode does not work reliably, especially with a system of inter-referencing formulas. When Excel stops the iterations, the system of inter-referencing cells can be left in an inconsistent state.