Return the independent variables in a symfun.
The counterpart of argname is formula:
argname for the independent
variables and formula for the dependent expression.
Examples:
syms x y f(x, y) = x^2; argnames(f) ⇒ (sym) [x y] (1×2 matrix)
See also: @symfun/formula, @symfun/symvar, findsymbols.
Package: symbolic