Jurnal Pembelajaran Matematika Inovatif ISSN 2614-221X (print) Volume 3, No. 2, Maret 2020 ISSN 2614-2155 (online) DOI 10.22460/jpmi.v3i1.p123-136 123 PENGEMBANGAN PERANGKAT PEMBELAJARAN BERBASIS MASALAH YANG MENGACU PADA LEARNING TRAJECTORY DAN BERORIENTASI PADA KEMAMPUAN JUSTIFIKASI MATEMATIS SISWA Alvi Khoirunnisak 1 , Ilham Rizkianto 2 1,2 Pendidikan Matematika UNY, Jl. Colombo No 1, Yogyakarta 1 alvi.khoirunnisak2015@student.uny.ac.id , 2 ilham_rizkianto@uny.ac.id Diterima: 2 Februari, 2020; Disetujui: 24 Maret, 2020 Abstract The present research and development project aims to develop and describe the quality of learning material consisting of lesson plans and student worksheets to facilitate student’s mathematical justification skills. The learning material is based on problem-based learning (PBL) approach and learning trajectory on the Cartesian Coordinate System. This project uses the ADDIE model (Analysis, Design, Development, Implementation, Evaluation). The subject of this research is 32 students in VIIIC SMPN 2 Bambang Lipuro. Based on the result of the validation assessment, the lesson plan and student worksheets are very valid. Based on the result of practicality using a student questionnaire, the learning material is practical. Based on the result of practicality using the observation sheet of learning implementation, the learning material is very practical. Based on the effectiveness assessment using the student’s mathematical justification skill test, 75% of students have minimum mathematical justification skills in the good category. However, based on the z-test, the learning material is not effective because z count = 0,6172 < z α =1,654. So, the learning material is valid and practice to be implemented, but not yet effective to facilitate student’s justification skills. It was possibly due to obstacles happening during the implementation, like the implementation of PBL needs more time than it planed, and some students did not do the writing task. Keywords: Learning material, PBL, Learning Trajectory, Mathematical Justification Skills Abstrak Penelitian ini adalah penelitian pengembangan yang bertujuan mengembangkan dan mendeskripsikan kualitas perangkat pembelajaran berupa RPP dan LKS berbasis problem based learning dan learning trajectory pada materi Sistem Koordinat Kartesius guna memfasilitasi kemampuan justifikasi matematis (KJM) siswa. Desain penelitian menggunakan model ADDIE (Analisys, Design, Development, Implementation, Evaluation). Subjek penelitian adalah 32 siswa kelas VIIIC SMPN 2 Bambang Lipuro. Berdasarkan penilaian kevalidan, RPP dan LKS dinyatakan sangat valid. Berdasarkan penilaian kepraktisan, RPP dan LKS dinyatakan praktis berdasarkan angket respon siswa dan dinyatakan sangat praktis berdasarkan observasi keterlaksanaan pembelajaran. Presentase banyaknya siswa yang mencapai kemampuan justifikasi pada kategori minimal tinggi sebesar 75%. Tetapi, perhitungan uji z menunjukkan z hitung =0,6172< z a =1,654. Dapat disimpulkan perangkat pembelajaran yang dikembangkan valid dan praktis, tetapi belum efektif dalam memfasilitasi KJM siswa. Hal ini diduga karena beberapa kendala yang dialami peneliti selama masa uji coba, seperti pembelajaran menggunakan metode PBL membutuhkan waktu lebih lama dari rencana dan adanya beberapa siswa yang tidak menyelesaikan tugas menulis. Kata Kunci: Perangkat Pembelajaran, PBL, Learning Trajectory, Kemampuan Justifikasi Matematis