Chapter 6.8, Problem 2P

Evaluate the line integral ${\displaystyle \oint (x+2y)}dx-2xdy$ along each of the following closed paths, taken counterclockwise:

(a) the circle $x^2+y^2=1;$

(b) the square with corners at $(1,1),(-1,1),(-1,-1),(1,-1);$

(c) the square with corners $(0,1),(-1,0),(0,-1),(1,0)$.