Aims and Research Questions Amid the current EdTech revolution, Extended Reality (XR) technology potentially represents a paradigm shift in the way humans interact with information. In varying degrees, it allows to digitally superimpose virtual images onto one's field of vision (Augmented Reality, or AR) - or fully digital immersion (Virtual Reality, or VR). Reality as we know it is thus poised to become a blend of physical and virtual objects. This has major implications for education, and in particular mathematical education, where visualisation of even complex concepts such as trigonometry plays a key role. The aim of this project, therefore, is to evaluate the facilitation of learning trigonometry using AR, VR and traditional paper-based resources pursuing the following Research Questions: Are there differences in mathematical performance outcomes between groups? If so, how are these linked to embodied experiences offered by the respective EdTech? Are there differences in attitudes towards learning between groups? If so, how are these linked to students' perceptions of access to/experiences of the concepts being learnt? Background and Context of this Research Within the rapidly growing corpus of research on XR in education, mathematics education studies highlight its association with improved performance outcomes, especially in secondary phases, as well as cognitive and affective gains for learners. If cognitive gains are linked to performance outcomes in mathematics, it seems that XR mediates these by providing enhanced, embodied experiences of the learning content. In fact, it was found that an AR environment allowing embodied interaction with the digitally augmented physical world had the strongest positive effects on 3D object manipulation. This aligns well with theoretical ideas on perception to action circuits and embodied cognition, which postulate that integration of bodily physical with visual information of the learning content, should improve cognitive representation and thus the accessibility of that content. Accordingly, the project will develop learning materials to mathematise a real-world, trigonometric problem: how sunlight varies with seasons. The learning materials will be designed to include incrementally scaffolded Earth-Sun models (in GeoGebra AR). Guidance levels and pace will be determined by instructors' formative assessment. They will progress from simple animations towards abstract geometric diagrams with auxiliary lines and labelled variables controlled by sliders This should facilitate the elusive algebraic reasoning ultimately needed to solve sunlight variation problems. Research Methods The project follows an experimental approach using a mixed-methods design and resource iteration in line with Design-Based Research paradigms to address the Research Questions in a three-stage procedure: Small-scale focus group on learning resources with mathematics teachers (to inform design tweaks) in which participants will be asked for feedback on Earth-Sun problems ranging from finding angles (single-step) to determining daylight hours (multi-step) in paper-pencil, but also AR and VR settings. Feedback will be sought on ease of problem visualisation, steps needed for optimal scaffolding, etc.. Intervention Study on Performances and attitudes in learning trigonometry with AR, VR and control group involving a pretest on prior knowledge of trigonometry and unscaffolded Earth-Sun problems followed by scaffolded instruction using worked examples. The post-test will involve worksheets from the pretest after using AR or VR applets as allocated as well as semi-structured interviews on perceptions, experiences, and affect during tasks; Impact Results of the project may pave the way for more widespread usage of XR in mathematics education providing a worked example ready for use in trigonometry lessons as more advanced curriculum content.