Septiati E, Hiltrimartin C, Hartono Y. Proof -Based Learning Design Using APOS Theory on Triangle Inequality Theorem Material. JELMaR [Internet]. 4Jan.2024 [cited 13Oct.2024];4(2):192-01. Available from: https://jelmar.wisnuwardhana.ac.id/index.php/jelmar/article/view/124