About: http://webisa.webdatacommons.org/210288752

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Although I knew the rotation formula earlier, the thing that clicked inside my head, by this answer, was that the angle is a constant (+/- 90), which simplicifies it to a simple negation and reversal of x and y.
http://www.w3.org/ns/prov#wasQuotedFrom	stackoverflow.com