Septiati E, Hiltrimartin C, Hartono Y. Proof -Based Learning Design Using APOS Theory on Triangle Inequality Theorem Material. JELMaR [Internet]. 2023 Nov. 23 [cited 2026 Aug. 25];4(2):192-203. Available from: https://jelmar.wisnuwardhana.ac.id/index.php/jelmar/article/view/163