Overview:  In this Explore, Jamal, Rashid, Sophie, and Mariana first locate three existing points on the map.  The students select three points based on the contextual information of the problem.  With the three points making a triangle, Sophie suggests they need to find bisectors of the sides of the triangle.  Rashid suggests using the angle bisectors, and Jamal says that the angle bisectors and the segments bisectors are given by the same lines.

Prior knowledge:  The students primarily rely on their prior knowledge of school mathematics.  Once they determine the three vertices of a triangle, the students discuss the strategy of using angle and/or segment bisectors to find the center of the triangle.  Jamal says that the angle bisectors and perpendicular bisectors in the triangle are the same, although this only happens in the special case of an equilateral triangle. 

Other points of interest:  Jamal, Rashid, Sophie, and Mariana do not seem to realize that angle bisectors and perpendicular bisectors are not in general given by the same segments in triangles.  Perhaps because the triangle students constructed looks approximately like an equilateral triangle, the students may be convinced that these are the same segments.  It is not clear whether students would recognize the difference between an angle and segment bisector if the triangle they created was more obviously not an equilateral triangle.