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