typos,start giac notes

quarto/alternatives/make_pdf.jl

@@ -5,6 +5,7 @@ module Make
 
 dir = "alternatives"
 files = (
+    "giac",
     "symbolics",
     "SciML",
     "plotly_plotting",

quarto/alternatives/symbolics.qmd

@@ -275,7 +275,7 @@ For example, `0+x` should simplify to `x`, as well `1*x`, `x^0`, or `x^1` should
 
   * `-x` becomes `(-1)*x`
   * `x * x` becomes `x^2` (and `x^n` if more terms). Meaning this expression is represented as a power, not a product
-  * `x + x` becomes `2*x` (and `n*x` if more terms). Similarly, this represented as a product, not a sum.
+  * `x + x` becomes `2*x` (and `n*x` if more terms). Similarly, this is represented as a product, not a sum.
   * `p/q * x` becomes `(p*x)/q)`, similarly `p/q * x/y` becomes `(p*x)/(q*y)`. (Division wraps multiplication.)