计ç®æ²çº¿ç§¯åâ«D(5x²-2y²+x²e³y)dx+(x³e³y-4xy+5y²)dy,å
¶ä¸D为ä¸ååå¨(x-1)²+y²=1,yâ§0,沿éæ¶éæ¹å.
解ï¼å°ç§¯åæ²çº¿Dçæ¹ç¨æ¹åæåæ°å½¢å¼ï¼Dï¼x=1+costï¼y=sintï¼0â¦tâ¦Ï
dx/dt=-sintï¼dy/dt=costï¼äºæ¯ï¼
(D)â«(5x²-2y²+x²e³y)dx+(x³e³y-4xy+5y²)dy
=[0ï¼Ï]â«{[5(1+cost)²-2sin²t+(1+cost)²e³sint](-sint)+[(1+cost)³e³sint-4(1+cost)sint+5sin²t]cost}dt
=[0ï¼Ï]{â«5(1+cost)²d(1+cost)+2â«sin³tdt-â«e³(1+cost)²(1-cos²t)dt-â«e³(1+cost)³costd(cost)
+4â«(1+cost)costd(cost)+5â«sin²td(sint)}
={(5/3)(1+cost)³-2[cost-(cos³t)/3]-e³â«[1+2cost-2cos³t-(cost)^4]dt-e³â«[cost+3cos²t+3cos³t+
+(cost)^4]d(cost)+4â«(cost+cos²t)d(cost)+(5/3)sin³t}[0ï¼Ï]
={(5/3)(1+cost)³-2[cost-(cos³t)/3]-e³[t+2sint-2(sint-(sin³t)/3)-(cos³tsint)/4-(3/4)(t/2+(1/4)sin2t)]
-e³[(1/2)cos²t+cos³t+(3/4)(cost)^4+(1/5)(cost)^5]+4[(1/2)cos²t+(1/3)cos³t+(5/3)sin³t}[0ï¼Ï]
={-2(-1+1/3)-e³[Ï-(3/4)(Ï/2)]-e³[(1/2)-1+(3/4)-(1/5)]+4[(1/2)-(1/3)}-{(40/3)-2(1-1/3)-e³Ã0
-e³[(1/2)+1+(3/4)+(1/5)]+4[(1/2)+(1/3)+0}
={4/3-(5/8)e³Ï+(1/20)e³+2/3}-{(40/3)-(4/3)-(49/20)e³+20/6}
=-40/3-(5/8)e³Ï-(12/5)e³=-40/3-(5Ï/8+12/5)e³
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