Ah, the principal branches... for sin inverse it's -π/2 to π/2, for tan inverse it's the same, but cos inverse is 0 to π. They say it's because cosine is decreasing there, so each value comes only once. But I always mixed them up—my notebook has more cashew sketches than formulas! My father, the schoolteacher, would sigh, "Sunil, *kay zhala*? You must focus." Now, trying to study again, I see those branches like the arms of our old tree: one goes this way, another that, and I'm still figuring out which way is mine.
#exams#study
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