Simple verification shows that when x? +y？ ≠0, partial derivative α p/α y = α q/α x, so in the simply connected region without coordinate origin, the curve integral has nothing to do with the path, and the alternative path is circle x? +y？ =2π? The parameter equation of the arc L 1 passing through 123 quadrants from point A to point B is X = √ 2π cost, Y = √ 2π Sint, and the value range of t is 5π/4 to -π/4, so the original integral = ∫ (5π/4 to-π/4) (.