The study examined students' mathematical reasoning skills in evaluating functions using GeoGebra in arithmetic sequence at senior high school

Mathematical reasoning ability remains relatively low, particularly in arithmetic sequence material that requires skills in recognizing patterns and evaluating functions. Therefore, it is necessary to apply the Inquiry-Based Learning method, assisted by GeoGebra, in the learning process. This study aims to describe students' mathematical reasoning abilities through Inquiry-Based Learning assisted by GeoGebra in evaluating arithmetic sequence functions in Grade XI of SMA Negeri 8 Palembang. The research employed a descriptive method with 28 students from Class XI.6 as subjects. Data were collected through a written test consisting of three essay questions based on mathematical reasoning indicators to measure students' ability to evaluate arithmetic sequence functions. Data analysis was conducted descriptively based on the indicators of students' mathematical reasoning abilities. The results showed that the average mathematical reasoning ability of students was in the good category, with a percentage of 68.9%. The distribution of students' abilities consisted of 39.29% (11 students) in the excellent category, 17.86% (5 students) in the good category, 39.29% (11 students) in the fair category, and 3.57% (1 student) in the poor category. Research findings indicate that the use of GeoGebra in inquiry-based learning supports students in understanding arithmetic sequences, evaluating functions, and determining the n-th term in a more structured and logical manner.