Let two non-zero vectors a and b act consecutively in the same plane.
(i) State the triangle law of vector addition.
(ii) Using position vectors, explain logically why a+b=b+a for any two vectors in the plane.
(iii) In a triangle ABC, suppose AB=a and BC=b. Express the vector AC in terms of a and b, and verify that the statement obtained is consistent with the triangle law mentioned in part (i).