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$$$x$$$ に関する $$$\ln\left(\frac{a^{2}}{x^{2}}\right)$$$ の導関数
関連する計算機: 対数微分計算機, 陰関数微分計算機（手順付き）
入力内容
$$$\frac{d}{dx} \left(\ln\left(\frac{a^{2}}{x^{2}}\right)\right)$$$ を求めよ。
解答
関数$$$\ln\left(\frac{a^{2}}{x^{2}}\right)$$$は、2つの関数$$$f{\left(u \right)} = \ln\left(u\right)$$$と$$$g{\left(x \right)} = \frac{a^{2}}{x^{2}}$$$の合成$$$f{\left(g{\left(x \right)} \right)}$$$である。
連鎖律 $$$\frac{d}{dx} \left(f{\left(g{\left(x \right)} \right)}\right) = \frac{d}{du} \left(f{\left(u \right)}\right) \frac{d}{dx} \left(g{\left(x \right)}\right)$$$ を適用する:
$${\color{red}\left(\frac{d}{dx} \left(\ln\left(\frac{a^{2}}{x^{2}}\right)\right)\right)} = {\color{red}\left(\frac{d}{du} \left(\ln\left(u\right)\right) \frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right)\right)}$$自然対数の導関数は $$$\frac{d}{du} \left(\ln\left(u\right)\right) = \frac{1}{u}$$$:
$${\color{red}\left(\frac{d}{du} \left(\ln\left(u\right)\right)\right)} \frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right) = {\color{red}\left(\frac{1}{u}\right)} \frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right)$$元の変数に戻す:
$$\frac{\frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right)}{{\color{red}\left(u\right)}} = \frac{\frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right)}{{\color{red}\left(\frac{a^{2}}{x^{2}}\right)}}$$定数倍の法則 $$$\frac{d}{dx} \left(c f{\left(x \right)}\right) = c \frac{d}{dx} \left(f{\left(x \right)}\right)$$$ を $$$c = a^{2}$$$ と $$$f{\left(x \right)} = \frac{1}{x^{2}}$$$ に対して適用します:
$$\frac{x^{2} {\color{red}\left(\frac{d}{dx} \left(\frac{a^{2}}{x^{2}}\right)\right)}}{a^{2}} = \frac{x^{2} {\color{red}\left(a^{2} \frac{d}{dx} \left(\frac{1}{x^{2}}\right)\right)}}{a^{2}}$$冪法則 $$$\frac{d}{dx} \left(x^{n}\right) = n x^{n - 1}$$$ を $$$n = -2$$$ に対して適用する:
$$x^{2} {\color{red}\left(\frac{d}{dx} \left(\frac{1}{x^{2}}\right)\right)} = x^{2} {\color{red}\left(- \frac{2}{x^{3}}\right)}$$したがって、$$$\frac{d}{dx} \left(\ln\left(\frac{a^{2}}{x^{2}}\right)\right) = - \frac{2}{x}$$$。
解答
$$$\frac{d}{dx} \left(\ln\left(\frac{a^{2}}{x^{2}}\right)\right) = - \frac{2}{x}$$$A