I'm not sure how to type it, so here's an image drawn using MS Paint:
It's an equals sign and a question mark superimposed on each other. From the times I've seen the symbol, it asks if the LHS is equal to the RHS. If yes, then [do something]. If not, then [do something else]. For example,
a =? b
If yes, then the proof is complete. If not, then we must have b < c ... [yada yada blah blah]
This symbol is not on Wikipedia, so I'm guessing it's nonstandard. If it is indeed nonstandard, then what is the most common way of expressing a =? b?
