This research aims to develop new didactic designs on line and angles materials for junior high school students. The didactic design is designed by considering several things: the result of the analysis of the learning instrument test obstacle, learning trajectory, and the didactical situation theory. This didactic design consists of four meetings obtained through three formal stages conducted during the reseacrh. The first stage is prospective analysis was didactic situation analysis before

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... rning in the form of hypothetical didactic design including ADP, the second metaper analysis was not the form of the design implementation stage, and the last was the retrospective analysis which was the analysis that correlates the prospective analysis with the metaproject analysis that was used to formulate the empirical didactic design. The research for preparing the didactic design began with a preliminary study which includes giving obstacle learning instrument tests, relevant thesis analysis, and a survey of students' mathematics textbooks. The didactic design was then implemented to 40 junior high school students of class VII. Based on the results of the research, didactic design that developed could be used as an alternative material teaching materials lines and angles to minimize student learning barriers.