Ethnomathematics in Bulang and Ampu: Exploring Geometric Concepts in Traditional South Tapanuli Wedding Accessories

Abstract

Ethnomathematics bridges formal mathematics and culturally embedded practices. This study identifies geometric concepts that can be defensibly inferred from visual evidence in representations of bulang and ampu, traditional South Tapanuli wedding accessories, and examines their potential as contexts for mathematics learning. A descriptive qualitative design employing ethnomathematics-based visual artifact analysis was used. Data comprised visual documentation of the Bulang and Ampu monuments at Alaman Bolak, Padangsidimpuan, the researchers' documentation, and relevant scholarly literature. Analysis involved inventorying visual features, coding them according to geometric concepts, comparing the codes with formal definitions, and triangulating interpretations against the literature. The findings indicate that bulang can be modeled in terms of triangles, trapezoids, angles, bilateral symmetry, and repetitive patterns. Ampu displays a conical-frustum form, circular structures, symmetry in its idealized basic form, and repetitive patterns. Translation, reflection, and rotation are more appropriately treated as didactic reconstructions through folding simulations than as direct empirical findings from monument images. The methodological contribution lies in distinguishing observable geometric evidence from pedagogical interpretations developed from cultural objects. These findings can inform contextual geometry activities while maintaining methodological caution in the interpretation of cultural artifacts.