1 files changed, 3 insertions(+), 3 deletions(-)

M blog/2019-02-23-resurracting-an-hp-7440a-plotter.markdown

@@ 1,6 1,6 @@
 ---
 layout: post
-title: "Resurrecting an HP 7440A plotter"
+title: "Resurrecting an old plotter"
 date: 2019-02-23
 comments: true
 tags: plotter, art, python, hardware, recurse


@@ 146,8 146,8 @@ A re-reading of the manual made us realize HP sold these functionality as an
 [hardware adaptor board that plugs in the
 bottom](https://support.hp.com/us-en/document/bpp01354), which we don't have.
 
-But everything in computer graphics is a line anyway right? With some [roots of
-unity](https://support.hp.com/us-en/document/bpp01354) we came up with a circle
+But everything in computer graphics is a line anyway right? With some [root of
+unity](http://mathworld.wolfram.com/RootofUnity.html) math, we came up with a circle
 drawing routine.
 
 <video width="600" height="450" controls>