My typical experience with examinations is that when a question expects a student to use a function provided in a previous question that the current question will make this explicit. I recently took an exam containing a question in which this was not the case and combined with some odd/incorrect phrasing due to English being this professors second language I was unable to answer a question worth a fairly significant amount of the overall grade due to this confusion.
Listening to some chatter as I left I noted that at least a few other students were also confused by the question and I realized shortly after leaving what the question should have been and that it would have been very straightforward to answer if it had been written more clearly. I even used the method it asked to demonstrate in a later question. I suspect that a significant majority of the other students figured out the intention of the question and answered it correctly.
I'm unsure what to do here, is it possible for a student to determine when a question is sufficiently unclear for it to be a problem?
The lecturer has also included impossible questions on graded assignments as well so I felt like it was not outside the realm of possibility for their to be a fatal error on an exam question.