If vector p +vector =vector r and vector,p=q=r then what is the angle between p and q

Vectors P Q and R have same magnitude.When vector P and Vector Q is added we get vector R ( using triangle law) we get a triangle PQR. Now as magnitude is same it is equilateral triangle. Therefore each angle is 60 degrees. In triangle law head of vector P is connected to tail of vector Q. But angle between two vectors is possible tail to tail. Hence shift Vector Q from head of vector P to tail of vector P without changing direction and keeping the shift parallel. This way we get the angle between vector P and Vector Q to be 120.