Jason K. Moore

I don't think there is a wrong answer because it was never perfectly specified what the answer would be. At this point, the input/output to the function is what is...

I agree with Oscar, this is expected behavior. We do have an msubs() function in the mechanics package. You could potentially do something there to align it with these common...

Also, you could make `find_dynamicsymbols()` smarter such that it detects unevaluated derivatives of expressions.

> All of these functions will work as intended if you use .doit(). I presume that you don't want to use .doit() because it does too much and makes the...

The broader issue is that we sometimes need `u(t)` to behave like a function of `t` (when taking derivatives) and sometimes we just want it to act like a generic...

The issue is that we only want to replace `f(t)` exactly, where the args of `Derivative(f(t), t)` would not count as an exact match because it is contained in an...

msubs tries to do too much and can be slow. I don't use it because of this. In general we are only ever making exact replacements (other than arguments to...

I don't have something at my finger tips and it is probably anecdotal memories from testing in the past. I don't see how msubs can be faster given that it...

This looks nice. My suggestion is that we add the example in the documentation. We can use numpy, scipy, and matplotlib in the docs. If we create an explanatory page...

In the tutorials directory: https://github.com/sympy/sympy/tree/master/doc/src/tutorials we should probably follow the directory structure of the sympy subpackages. For example there is a `sympy/vector` and `sympy/physics/vector`, so for long term organization, we...