This paper investigates the triangular and polygonal formation control problem for mobile multi-agent systems under the constraint that each agent can only take angle measurements. For triangular formations, due to the fact that the sum of three interior angles always equals pi, the desired triangular shape can be obtained when any two agents achieve desired angles for which they are the corresponding vertices of the triangle. So to achieve the desired shape of a triangular formation, we propose to let one agent remain fixed and the other two agents move along their bisectors respectively with respect to their two neighbors. For convex polygonal formations, since the sum of all interior angles is constant, we are able to use a similar contr...