Ethnomathematics Exploration of the Toba Community: Elements of Geometry Transformation Contained in Gorga (Ornament on Bataks House)

Gorga is an ornament known to the Batak community. As one of the works of art that poured in the form of carvings, gorga become icons for batak society. Long before the Batak people knew formal education, they had made gorga. This is evidenced through several historical sources. Gorga not only contains the value of art but also has a mathematical element. There are many mathematical principles used in the process of making gorga. The principle of geometry transformation is very prominent in the gorga motifs. This article is an ethnomathematics research that will discuss how the thinking process in making gorga. Observations and interviews with the gorga craftsmen (pande) are conducted to find out how the principles of rotation, translation, dilation and reflection are used in making gorga motif