I am just starting to read up on differential equations. The problem is (in my materials) nowhere is explained what do these dots mean. Can anyone shed some light?
$$\begin{align}&\begin{cases} \dot x=2x+y ,\\ \dot y=3x+4y. \\ \end{cases} \\ &\begin{cases} \dot x+x-8y=0, \\ \dot y-x-y=0. \\ \end{cases}\end{align}$$
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$\begingroup$It usually means derivative with respect to time. The notation goes back to Newton.
By the way, $\ddot{x}$ is often used in Physics for the second derivative of $x$ with respect to time.
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