I.4.34 Curvilinear Integrals

Condition: Calculate the following curved integral of the 2nd kind, taken along the indicated curves in the direction of the parameter: \ \ oint_ {c} \ frac {(x+y) d x- (x-y) d y} {x^{2}+y^{2} \] where \ (c-) the circle \ (( x^{2}+y^{2} = a^{2} \), running against the course of the watch.