Abstract. Teacher’s communication skill plays an important role, one of which is to guide a class discussion for teaching purposes. This study aimed to investigate a teacher’s mathematical communication profile in facilitating and guiding a class discussion. This study is qualitative. A junior teacher of high school (i.e., a teacher with 1 to 5 year teaching experience) teaching mathematics at X-Social Class was selected as the subject of this study. The data was collected by observing the teacher’s mathematical communication in facilitating and guiding a discussion with the rules of sinus as the teaching material, and it was followed by a deep interview. The result showed that the junior teacher facilitated and guided a class discussion through 3 processes, which consisted of (1) anticipating any kinds of methods the students might propose to solve problems dealing with the rules of sinus, (2) paying intention on to what extent the students were involved in solving problems, and (3) asking one student to present his/her work, based on assessment and contribution of their works in order to reach the teaching purposes.

Keywords: Mathematical Communication, Junior Teacher, Facilitating and Guiding a Class Discussion.