Mathematical arguments in mathematics learning make students express opinions in accordance with what they believe as the facts. So argument is important in solving math problems. Students must be able to unfold their arguments while solving problems. Students can put forward good reasons by searching for relevant data on their claims.

 

This study aims to investigate the ability of students' mathematical argument related to solving plane. Two volunteer students of the junior high school 5th grade who have the same ability were chosen as research subjects. Selected students were given tests related to the geometry.

 

The results of the test were analyzed and semi-interviews were conducted on the two students. From the test results found that students can not apply their arguments into writing. This is because they do not know the steps to apply the argument in solving the problem. During the interview, students can be held accountable for what they write. This means they can argue verbally. So that students do not have difficulty in solving problems geometry. From the results of this study should students be taught about the procedure of argument in mathematics, so that in solving the problem can be solved properly and correctly.