od Daniel » Subota, 16. Mart 2013, 04:01
Kad imamo funkciju ovakvog oblika, onda je napišemo kao [inlmath]f\left(x\right)=e^{\ln f\left(x\right)}[/inlmath], pa od toga tražimo izvod:
[dispmath]f\;'\!\left(x\right)=\left[\left(1+x\right)^x\right]'=\left[e^{\ln\left(1+x\right)^x}\right]'=\left[e^{x\ln\left(x+1\right)}\right]'=[/dispmath][dispmath]=e^{x\ln\left(x+1\right)}\cdot\left[x\ln\left(x+1\right)\right]'=e^{x\ln\left(x+1\right)}\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right][/dispmath][dispmath]f\;''\!\left(x\right)=\left\{e^{x\ln\left(x+1\right)}\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]\right\}'=[/dispmath][dispmath]=\left[e^{x\ln\left(x+1\right)}\right]'\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]+e^{x\ln\left(x+1\right)}\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]'=[/dispmath][dispmath]=e^{x\ln\left(x+1\right)}\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]+e^{x\ln\left(x+1\right)}\cdot\left[\frac{1}{x+1}+\frac{x+1-x}{\left(x+1\right)^2}\right]=[/dispmath][dispmath]=e^{x\ln\left(x+1\right)}\cdot\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]^2+e^{x\ln\left(x+1\right)}\cdot\left[\frac{1}{x+1}+\frac{1}{\left(x+1\right)^2}\right]=[/dispmath][dispmath]=e^{x\ln\left(x+1\right)}\left\{\left[\ln\left(x+1\right)+\frac{x}{x+1}\right]^2+\frac{1}{x+1}+\frac{1}{\left(x+1\right)^2}\right\}[/dispmath]
Ajd pokušaj dalje da nađeš treći, ako treba i četvrti izvod, to je sad dalje zaista naporan, ali čisto fizički posao... I pokušaj da među tim izvodima nađeš neku pravilnost...
I do not fear death. I had been dead for billions and billions of years before I was born, and had not suffered the slightest inconvenience from it. – Mark Twain