Merge pull request #533 from cmbuckley/catenary-svg

Replace catenary figure with SVG version

Author: cmbuckley

_posts/2007-08-05-square-wheels-and-catenary-roads.md

@@ -11,11 +11,11 @@ image:
     src: /files/2007/08/road-real.jpg
     alt: Model of a catenary road
 shortlink: bswcr
-last_modified_at: 2021-08-19 22:46 +01:00
+last_modified_at: 2025-08-29 19:17 +00:00
 ---
 The other day [Paul](https://pictures.scholesmafia.co.uk/index.php/?profile=150) told me that square wheels (and, indeed, any regular polygon except a triangle) can {% include archive.html url="http://www.maa.org/mathland/mathtrek_04_05_04.html" text="ride on a road constructed of inverted catenaries" %}. A catenary is the curve made by a telegraph wire when stretched between two poles --- a cable hanging under its own weight.
 
-{% include figure.html img="/files/2007/08/catenary.png" alt="Inverted catenary with height to the vertex labelled h" %}
+{% include figure.html object="/files/2007/08/catenary.svg" alt="Inverted catenary with height to the vertex labelled h" %}
 
 A little bit of thinking about the road makes you realise that the length of the catenary _s_ must be the same as the length of the side of the square, and the height _h_ must be