About: http://webisa.webdatacommons.org/217781455

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	I think that it happens for angle=k*pi where k is an integer with the possible values: 0, 1, 2, 3...
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com