Trigonometry is an area of mathematics that students believe to be particularly difficult and/or abstract compared to other areas of mathematics. It is introduced as the concept in the right-angled triangle from the basic level, but the curriculum of Nepal introduced it from grade nine onwards as a separate chapter. Its content area has a weighting of nearly one-fourth of the part in additional mathematics and around 10% in compulsory mathematics. This study aims to explore students' experiences in learning trigonometry. The data are extracted from twelve grade ten students who had chosen additional mathematics in their optional courses. Formal and informal interviews, diagnostic tests, and in-depth engagement with students in their classrooms were the major sources of data extraction. In this sense, this study adopted phenomenology as a methodological stance. The data collected from the diagnostic test were analyzed, and students' explanations of each question were discussed in this study. In doing so, this study concludes with some major findings. Students have difficulty learning trigonometry and have misconceptions about the basic concepts, producing obstacles and errors in solving trigonometric problems. The possible errors are in procedural knowledge, conceptual knowledge, or link between these two types of knowledge. It is also found that a teacher needs to incorporate the learners' everyday experiences using materials, diagrams, and equipment for meaningful learning and long-lasting knowledge. A teacher needs to be aware and responsible for students' activities inside the classroom. Healthy relationships between the teacher and the students can significantly contribute to learning trigonometry.