Evaluate the line integral
with and constants, along each of the following paths between the points and :
(i) the straight line between and ;
(ii) the -axis from to the origin followed by the -axis to ;
(iii) anti-clockwise from to around the circular path centred at the origin .
You should obtain the same answer for the three paths when . Show that when , the integral takes the same value along any path between and .