Ableitung von $$$\ln\left(\cos{\left(x \right)}\right)$$$
Ähnliche Rechner: Rechner für logarithmische Differentiation, Rechner zur impliziten Differentiation mit Schritten
Ihre Eingabe
Bestimme $$$\frac{d}{dx} \left(\ln\left(\cos{\left(x \right)}\right)\right)$$$.
Lösung
Die Funktion $$$\ln\left(\cos{\left(x \right)}\right)$$$ ist die Komposition $$$f{\left(g{\left(x \right)} \right)}$$$ der beiden Funktionen $$$f{\left(u \right)} = \ln\left(u\right)$$$ und $$$g{\left(x \right)} = \cos{\left(x \right)}$$$.
Wende die Kettenregel $$$\frac{d}{dx} \left(f{\left(g{\left(x \right)} \right)}\right) = \frac{d}{du} \left(f{\left(u \right)}\right) \frac{d}{dx} \left(g{\left(x \right)}\right)$$$ an:
$${\color{red}\left(\frac{d}{dx} \left(\ln\left(\cos{\left(x \right)}\right)\right)\right)} = {\color{red}\left(\frac{d}{du} \left(\ln\left(u\right)\right) \frac{d}{dx} \left(\cos{\left(x \right)}\right)\right)}$$Die Ableitung des natürlichen Logarithmus ist $$$\frac{d}{du} \left(\ln\left(u\right)\right) = \frac{1}{u}$$$:
$${\color{red}\left(\frac{d}{du} \left(\ln\left(u\right)\right)\right)} \frac{d}{dx} \left(\cos{\left(x \right)}\right) = {\color{red}\left(\frac{1}{u}\right)} \frac{d}{dx} \left(\cos{\left(x \right)}\right)$$Zurück zur ursprünglichen Variable:
$$\frac{\frac{d}{dx} \left(\cos{\left(x \right)}\right)}{{\color{red}\left(u\right)}} = \frac{\frac{d}{dx} \left(\cos{\left(x \right)}\right)}{{\color{red}\left(\cos{\left(x \right)}\right)}}$$Die Ableitung des Kosinus ist $$$\frac{d}{dx} \left(\cos{\left(x \right)}\right) = - \sin{\left(x \right)}$$$:
$$\frac{{\color{red}\left(\frac{d}{dx} \left(\cos{\left(x \right)}\right)\right)}}{\cos{\left(x \right)}} = \frac{{\color{red}\left(- \sin{\left(x \right)}\right)}}{\cos{\left(x \right)}}$$Vereinfachen:
$$- \frac{\sin{\left(x \right)}}{\cos{\left(x \right)}} = - \tan{\left(x \right)}$$Somit gilt $$$\frac{d}{dx} \left(\ln\left(\cos{\left(x \right)}\right)\right) = - \tan{\left(x \right)}$$$.
Antwort
$$$\frac{d}{dx} \left(\ln\left(\cos{\left(x \right)}\right)\right) = - \tan{\left(x \right)}$$$A