Samkvæmt reglum sem gilda um rétthyrnda þríhyrninga fæst:[br] cos(v) = x/1 = x[br] sin(v) = y/1 = y[br] tan(v) = y/x = sin(v)/cos(v)[br]Þá fæst:[br] cos(v) = x hnit punkts[br] sin(v) = y hnit punkts[br] tan(v) = sin(v)/cos(v), (cos(v) má ekki vera 0)