Ethnomathematical Exploration of the Tutup Ari Ornament at Padangsidimpuan City Park: Plane Geometry Concepts and Their Potential as a Contextual Learning Resource

Abstract

This study explores plane geometry concepts represented in the Tutup Ari ornament at Padangsidimpuan City Park and examines its potential as a contextual mathematics learning resource. A qualitative descriptive-exploratory design was employed within an ethnomathematics framework. Data were collected through direct observation, photographic documentation, and a literature review on ethnomathematics, Angkola-Mandailing decorative traditions, and contextual mathematics learning. Analysis involved segmenting visual elements, superimposing geometric guide lines, identifying geometric properties, classifying shapes, and interpreting their relationship with local decorative motifs. The findings identified six principal geometric concepts: triangles in Bindu Matogu/Ador-ador Duri-duri, rhombi in Suncang Duri/Raga-raga, trapezoids and parallelograms in Singgor, rectangles in Silindung, and circles in Mataniari. The patterns also demonstrate repetition, parallelism, regularity, and visual symmetry. The novelty of this study lies in using a publicly accessible replica of Tutup Ari as a learning context that supports observation, measurement, representation, and geometric reasoning. Padangsidimpuan City Park therefore has potential as an open-air learning laboratory connecting school mathematics with local culture. However, this study was limited to visual exploration and did not assess instructional effectiveness among students.