## 1 Introduction  
[PERSON] [1] described ethomathematics as \"the mathematics which is practised among identifiable cultural groups, such as national-tribal societies, labor groups, children of a certain age bracket, professional classes, and so on\" (p. 45). The adoption of an ethomathematical perspective in developing informal mathematical curricula ensures that both contextualized problems and students' cultural links and are considered [2]. This function of ethomathematics is satisfied by implementing a culturally relevant pedagogy in the school curriculum, which helps to increase students' cognitive and emotional aptitude [3]. In addition, it helps students understand the role that mathematics plays in a societal context [4]. The ethomathematics perspective was applied in different countries with different groups of students, from different ages, where these students made connections between ethno-contexts and school mathematics. For example, [PERSON] [5] reported that using contextualized problems to teach primary students, from Pacific Island nations that live in New Zealand, enhanced their understanding of decimal numbers. The ethomathematics context was utilized to emphasize the multi-culturalist feature of knowledge, especially mathematical knowledge [6]. [PERSON], [PERSON], and [PERSON] [7] reported that high school students found the construction of geometrical ornaments, from different cultures in Israel, and the discovery of their mathematical properties to be both meaningful and enjoyable. In addition, the construction of geometrical ornaments can foster creativity and lead to deep inquiry from both mathematical and cultural perspectives [7]. Furthermore, [PERSON], and [PERSON] [8] found that ethnomathematics-oriented materials improved the mathematical understanding of participating students in Indonesia. [PERSON] [9] reported that the implementation of ethnomathematical unit on measurement (area, perimeter, volume) facilitated the understanding of mathematical concepts among fifth-grade students in the Maldives, which was done through practical examples using cultural objects, investigations, and by relating school mathematics to real world activities. This relatedness motivated and interested the students to learn mathematical concepts. [PERSON] and [PERSON] [10] reported that integrating ethnomathematics instructional approach affected positively the acquisition of creative skills among Nigerian students.  
Geometry is considered the core of culture and ethnomathematics [11; 12], whereas art connects the two. Art is considered an important code for cultural groups, and it can serve as a powerful tool for teachers in the classroom [13]. This is particularly true for Islamic art, the most dominant aspect of which is its ornamentation [14]. In the current study, we used Islamic geometrical ornamentation to design ethnomathematics learning regarding triangle congruence. The triangle congruence theorems are one of the essential topics in classical geometry [15], but students often struggle to understand it [16]. Little research has been done on the teaching of congruence; at least, little research that is written in English [17] or is related to learning the concept of congruence, especially with regard to reasoning and proof [18]. The lack of research already carried out on triangle congruence, in addition to its importance and its complexity, led us to choose this topic for the current study. The main aim of the study is to examine the effect of ethnomathematics on the learning of triangle congruence by middle school students who carry out activities based on Islamic geometrical ornamentation.