Practicing Success
If $f(x)=|\log _e|x||$, then f'(x) equals |
$\frac{1}{|x|}, x \neq 0$ $\frac{1}{x}$ for $|x|>1$ and $-\frac{1}{x}$ for $|x|<1$ $-\frac{1}{x}$ for $|x|>1$ and $\frac{1}{x}$ for $|x|<1$ $\frac{1}{x}$ for $x>0$ and $-\frac{1}{x}$ for $x<0$ |
$\frac{1}{x}$ for $|x|>1$ and $-\frac{1}{x}$ for $|x|<1$ |
For x > 1, we have $f(x)=|\log | x||=\log x \Rightarrow f'(x)=\frac{1}{x}$ For x < -1, we have $f(x)=|\log |x||=\log (-x) \Rightarrow f'(x)=\frac{1}{x}$ For 0 < x < 1, we have $f(x)=|\log |x||=-\log x \Rightarrow f'(x)=-\frac{1}{x}$ For -1< x < 0, we have $f(x)=-\log (-x) \Rightarrow f'(x)=-\frac{1}{x}$ Hence, $f'(x)=\left\{\begin{aligned} \frac{1}{x}, & |x|>1 \\ -\frac{1}{x}, & |x|<1\end{aligned}\right.$ |