On a lighter note, you can tell the discipline of the writer by their notation (OK, only slightly better than chance).
- Mechanical engineers like ##\xi##. I can't fathom why. Since it's not nearly as pretty as...
- Q. Which means you're probably an EE. Although you would grudgingly acknowledge that they are really the same thing.
- If you use ##\xi## or Q but they are an element of a matrix in equations with only one derivative, then you are definitely, absolutely, a controls engineer. You worship the word "state space" as if it was Yahweh.
- If your equations are full of n, (n-1), and (n-2), but no derivatives, then you are a DSP control guy. You don't need ##\xi## or Q, everything is ##a_n##, ##a_{n-1}## and such. Half of you thought I should have said k, (k-1), and (k-2). Half of you have never touched the hardware you are controlling with your code. Time is just a constant called ##T##, which appears everywhere but is ignored.
- ##\delta##: probably a mathematician. Since you never see it in an engineering book.
- If an engineer doesn't even recognize it's a SHO equation, like
this, then you are definitely a physicist. Although you use ALL of the other notations too, except the discrete time stuff.
- If you are a biologist, geologist, or chemist, then you don't care and aren't sure where your textbook is with this material. But you know you have it, you knew it, and could relearn it if you can't find a friend to do it for you.
But... It's all the same thing.