摘要：Mathematical problem solving ability is one of the most important abilities students must have to process the information provided in solving problems. Before using mathematical problem solving skills, prior knowledge becomes the most crucial thing that makes students able to connect all available information so that they can construct new knowledge through the process of assimilation or accommodation.The purpose of this reseach is to:(1) Analyze prior knowledge what student has so the student can solve the problem of tangent circle given; (2) Know how learning trajectory in student’s mathematical problem solving ability by applying metacognition approach. This reaseacrch is a design research to improve the quality of learning. In this reseacrh researchers gave 3 test questions on students’ mathematical problem solving abilities. One trial was conducted in class VIII-B and trial II was conducted in class VIII-A, each consisting of 30 students junior high school. The result of students answer analysis shows the mast problematic topic that makes the studnts are difficult to solve the problem is about the tangent cicrcle that is the elements of the circle and the concept of circle circumtance there are three phased in learning path of students mathematical problem solving skill that are under standing the problem, making the problem solving plan by prrior knowledge and doing problem solving and evaluating it. From this explanation, it is better for teachers to ensure students have sufficient prior knowledge to make it easier to construct new knowledge, as well as make the learning process fun and meaningful so that students will remember knowledge in long-term memory.
关键词：mathematical problem solving skill; prior knowladge; circle tangent; metacognition approach
