move over MTK low level symbolic doc details to Symbolics

docs/src/getting_started.md

@@ -196,6 +196,17 @@ convert the output to an `Expr`:
 Symbolics.toexpr(x + y^2)
 ```
 
+The other way around is also possible, parsing Julia expressions into symbolic expressions
+
+```@example symbolic_basics
+ex = [:(v ~ w)
+      :(w ~ -v)]
+eqs = parse_expr_to_symbolic.(ex, (Main,))
+eqs_lhs = [eq.lhs for eq in eqs]
+eqs_rhs = [eq.rhs for eq in eqs]
+Symbolics.jacobian(eqs_rhs, eqs_lhs)
+```
+
 ## `Sym`s and callable `Sym`s
 
 In the definition

docs/src/manual/faq.md

@@ -88,3 +88,31 @@ be selected (since `x == y` is unknown for arbitrary symbolic values!). This is
 required, since this is a non-lazy check of whether the symbol `x` is always equal to the symbol `y`, rather than
 an expression of whether `x` and `y` currently have the same value.
 
+## Understanding the Difference Between the Julia Variable and the Symbolic Variable
+
+In the most basic usage of Symbolics, the name of the Julia variable
+and the symbolic variable are the same. For example, when we do:
+
+```@example faq
+@variables a
+```
+
+the name of the symbolic variable is `a` and same with the Julia variable. However, we can
+de-couple these by setting `a` to a new symbolic variable, for example:
+
+```@example faq
+b = only(@variables(a))
+```
+
+Now the Julia variable `b` refers to the variable named `a`. However, the downside of this current
+approach is that it requires that the user writing the script knows the name `a` that they want to
+place to the variable. But what if for example we needed to get the variable's name from a file?
+
+To do this, one can interpolate a symbol into the `@variables` macro using `$`. For example:
+
+```@example faq
+a = :c
+b = only(@variables($a))
+```
+
+In this example, `@variables($a)` created a variable named `c`, and set this variable to `b`.