Integrating $\frac{df}{f}$ I know the general solution to $\dfrac{df}{dt}=f$ is $f(t)=e^tC$. But how does one compute it from integrating both sides of $\dfrac{df}{f}=dt$? The left part does not seem to make any sense!

$$\int\frac{df}{f}=\log\left(|f|\right)=\int dt=t+C_1$$
so
$$f=Ce^t$$
where $C=\pm e^{C_1}$
