C1　： 　r(t) = ( t , 0 , 0 ) ( 3 <= t <= 3 )
C2　：　 r(t) = ( 3cos t , 3sin t , 0 ) ( 0 <= t <= π )
a = ( x^2 , y , -z )

dr=(1,0,0)dt
a=(t^2,0,0)
a*dr=(t^2,0,0)*(1,0,0)dt=t^2dt=t^3/3 (-3->3)=9+9=18

∫c1 a・dr = 18

∫c1+c2 a・dr = 0