First, please post real code that shows the problem. Descriptions of code isn't good enough -- we would like to see the actual code that you're attempting to run.
Secondly, order can matter, even though the different ordering should give you an equivalent answer if you calculated by hand. If you were to do the research, you will see many classical shool-book formulas have to be rewritten so that computing machines do not produce zero-divides, singularities, etc.
- a multliplication of two numbers (a binary *)
- a reference to the content pointed by an address (a unary *)
Here, it seems the compiler is considering that the star is used for the second purpose, for some reasons I dont know until I can see the code (my guess is that there is a ";" at the end of #define PI ..., and this is not important if PI is used at the end of the formula, but it matters if PI is used before the end).