1ã对äºä»»æçxï¼0ï¼åå½æ°f(t)ï¼arctantï¼tâ[0ï¼x].
f(x)ï¼f(0)ï¼f'(ξ)Ãxï¼Î¾â(0ï¼x).
å³arctanxï¼x/(1ï¼Î¾^2).
1/(1ï¼x^2)ï¼1/(1ï¼Î¾^2)ï¼1ï¼æ以ï¼x/(1ï¼x^2)ï¼arctanxï¼x.
2ãåå½æ°f(x)ï¼lnxï¼xâ[aï¼b]
f(b)ï¼f(a)ï¼f'(ξ)Ã(bï¼a).
f'(ξ)ï¼1/ξâ(1/bï¼1/a)ï¼æ以ï¼(bï¼a)/bï¼lnbï¼lnaï¼(bï¼a)/aï¼å³
(bï¼a)/bï¼ln(b/a)ï¼(bï¼a)/a
3ã设f(x)ï¼arctanxï¼arccotxï¼xâ(ï¼âï¼ï¼â).
f'(x)â¡0ï¼æ以f(x)â¡Cï¼å¸¸æ°ï¼.
åf(0)ï¼Ï/2ï¼æ以Cï¼Ï/2.
æ以ï¼arctanxï¼arccotxï¼Ï/2.
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