Update first part of boundary values chapter

Author: mfherbst

src/09_Numerical_differentiation.jl

@@ -936,19 +936,11 @@ md"""
     In this case, we are approximating a second derivative, so the derivation order is 2, and it turns out that this formula has an approximation error in $\mathcal O (h^2)$ so the approximation order is also 2.
 """
 
-# ╔═╡ 9ff5697a-90a0-4fb3-a93b-e99e3c14b11e
-md"""
-## Side-stepping the finite precision problem: Going complex
-
-TODO("Include this fantastic remark by Nick Highham:
-
-https://www.siam.org/publications/siam-news/articles/differentiation-without-a-difference
-")
-
-"""
+# ╔═╡ b6418149-6c31-44d7-a8d3-95d8418daa59
+md"Show outline $(@bind show_outline CheckBox(default=true))"
 
 # ╔═╡ 9c8ad9b0-50eb-478e-b63c-26a868765230
-let
+if show_outline
 	RobustLocalResource("https://teaching.matmat.org/numerical-analysis/sidebar.md", "sidebar.md")
 	Sidebar(toc, ypos) = @htl("""<aside class="plutoui-toc aside indent"
 		style='top:$(ypos)px; max-height: calc(100vh - $(ypos)px - 55px);' >$toc</aside>""")
@@ -2619,7 +2611,7 @@ version = "1.13.0+0"
 # ╟─ca3564d3-059e-40ce-bbcd-a04594e8ac24
 # ╟─56368f98-6f51-49be-8333-6fa1b9c64cf1
 # ╟─2adfac60-ec91-4c70-ae0c-f460f47d37dc
-# ╠═9ff5697a-90a0-4fb3-a93b-e99e3c14b11e
+# ╟─b6418149-6c31-44d7-a8d3-95d8418daa59
 # ╟─9c8ad9b0-50eb-478e-b63c-26a868765230
 # ╟─00000000-0000-0000-0000-000000000001
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