Some sort equation ... tommy1729 Ultimate Fellow Posts: 1,859 Threads: 402 Joined: Feb 2009 10/15/2015, 12:12 PM I was thinking about the sign of the n th Derivative. More precisely real analytic for x>0 where the expansion point Goes from 0 to + oo. Sine and cosine are simple. But for other cases , when the expansion point Goes to + oo it is less trivial. For instance - too give a quite general case - What about e.g. D^a(n) f(b(m)) < 0 D^a2(n) f(b2(m)) > 0. What are the solutions and how to find them easily ? Maybe this is easy sorry. I havent thought about it much. Regards Tommy1729 « Next Oldest | Next Newest »

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