Student’s triangles congruence proving through flow proof strategy

Abstract The purpose of this study is to describe students proving congruence triangles. Proving congruence is a prerequisite to develop skills in constructing formal proof in mathematics. The subject in this study are 33 students of SMP Negeri 33 grade IX.1. The Learning process implemented with flow proof strategy, namely re-writing existed information, stating what is needed to be proved, using existed rules such as postulate and definition, and writing the consequence from used rules. Data were collected by a test with three questions and interviews. The results show that students know step by step in writing the proofs after the implementation of flow proof strategy and students’ ability on congruence proving in class nine SMP N 33 Palembang categorized satisfactory, with 4% of the students categorized as excellent, 16% in good, 48% in satisfactory, 24% in poor, and 8% in very poor category. Generally, students’ obstacle in proving is in determining rules that will be applied for constructing a proof and not understand what is to be proof. Other error in proving is writing symbols.