A Trigonometric function is one of the challenging materials for not only high school students but also pre-service teachers and teachers. On the other hand, An understanding of trigonometric function is an initial stage in understanding calculus derived from it such as limit, derivative, and integral. Thus, the competency in trigonometric function is an issue need further discussion. This is a qualitative study which elaborated the didactical design and the class observation of high school student. In this study, we propose a didactical design with the aim to figure out the properties of trigonometric functions. Starting from drawing the graph then analyse each of the graphs. We used the trigonometric function graph as a media to analyse the function such as trigonometric value, maximum and minimum, period, and interval in which it decreases or increases. The two main aims in this study are: 1) How the unit circle is used for drawing trigonometric function graph, 2) How the trigonometric function graph can be used to analyse the trigonometric function properties. The study shows that the students can follow the learning sequences both in drawing and analysing the graph. The misconception of trigonometric values is figured out. Some unpredictable findings are also described in this study.
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