(本题满分12分)设函数\(f(x)\)在\(x = 0\)处连续,且\(\lim\limits_{x \to 0}\frac{xf(x) - e^{2\sin x} + 1}{\ln(1 + x) + \ln(1 - x)} = - 3\)。证明\(f(x)\)在\(x = 0\)处可导,并求\(f^\prime(0)\)。
解: 已知\(\ln(1 + x...
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解:已知\(\ln(1 + x) + \ln(1 - x)=x - \frac{1}{2}x^2 + o(x^2) - x - \frac{1}{2}x^2 + o(x^2)= - x^2 + o(x^2)\)\(e^{2\sin x}=1 + 2\sin x + \frac{1}{2}(2\sin x)^2 + o(x^2)=1 + 2\sin x + 2\sin^2 x + o(x^2)\)因此,\(-3 = \lim\limits_{x \to 0}\frac{xf(x) - e^{2\sin x} + 1}{-x^2}=\lim\limits_{x \to 0}\frac{xf(x) - (1 + 2\sin x + 2\sin^2 x + o(x^2)) + 1}{-x^2}\)\(=\lim\limits_{x \to 0}\frac{xf(x) - 2\sin x}{-x^2} + \lim\limits_{x \to 0}\frac{-2\sin^2 x}{-x^2}\)可以得出\(\lim\limits_{x \to 0}\frac{xf(x) - 2\sin x}{-x^2} = - 5\),\(\lim\limits_{x \to 0}\frac{xf(x) - 2\left(x - \frac{1}{6}x^3 + o(x^3)\right)}{x^2} = 5\),进一步可以得出\(\lim\limits_{x \to 0}\frac{xf(x) - 2x}{x^2} = 5\),以及\(\lim\limits_{x \to 0}\frac{f(x) - 2}{x} = 5\),\(\lim\limits_{x \to 0}[f(x) - 2] = 0\),可得\(\lim\limits_{x \to 0}f(x) = 2 = f(0)\),故\(f^\prime(0) = \lim\limits_{x \to 0}\frac{f(x) - 2}{x} = 5\) 。
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