Siyini isamba sama-engeli kunxantathu?
Ngokuvamile sibheka lokhu esikhaleni se-Cartesian esinobukhulu obubili, esibizwa nangokuthi 'i-Euclidian geometry'. Kulokhu isamba sama-engeli kunxantathu ngaso sonke isikhathi siwu-180 degrees. Kukhona namanye ama-geometry lapho lokhu kungenjalo ngempela. Isibonelo esikhaleni esinobukhulu obuthathu esakhiwe njengebhola ungaba nonxantathu ebusweni bebhola lapho isamba sama-engeli singama-degree angama-270.