When you are taking up an exam that is not written in 丁寧語 but rather in dictionary form, and it requires a brief answer from you (for example, the problem you have to answer is simply 「理由：」 ), are you required to answer in 丁寧語／ます形？ Any insights on answering exams written in Japanese?
Does not really matter how is written the exam, you do not need to answer in ます形.
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1Probably related, ます形 is almost never used (I haven't seen any and I believe I won't) in scientific articles/papers. – Yosh Apr 4 '15 at 16:25
