The purpose of this study is to set up a hypothetical learning trajectory (HLT) in graph drawing among trigonometric functions, to check at what level of HLT students make misunderstanding, and to find the reason. In addition, it is to study what kind of tasks are set and how to solve these misunderstanding. For HLT setting, various misunderstanding or error data were collected through literature study, and the HLT level of graph drawing was set by analyzing it. Based on this level, a diagnostic test was performed on 11 students and the developmental level of the students was categorized. Two of them were selected to execute a task for solving misunderstanding and the results were observed. Find of misunderstanding based on HLT level and tasks for solving them were effective.