Assertion: right triangle's side | /r/CapableOf | imply three rational cosines
Facets:
value: by the law of cosines
type: OTHER
Source sentences:
text: This is because integer sides imply three rational cosines by the law of cosines, and by Niven's theorem a rational cosine coincides with a rational angle if and only if the cosine equals 0, ±1/2, or ±1.