?x2?y2?ax?0,y?0??exa2?y2dxdy?20??d??erdr0r2?1?r?a??e22??0?a2
?4(e?1)2(4分)[69][答案]
???rsin??rdrd?D?20??sin?d???r2dr0aa3?1?3a3?3(3分)[70][答案]
53
??d??02?221rdr2382?2??(r3)1845??4?4
(3分)[71][答案]
x2?y2?42???dxdy?2x2?y2?4??(x2?y2)dxdy?16???d??r3dr00
?16??2???8?164(5分)[72][答案]
???3d??02cos?1r3cos?sin?dr1??3(4cos5?sin??cos?sin?)d? 0419?6(5分)[73][答案]
????r2e?rsin?cos??rdrd?D2?20??sin?cos?d??r3e?rdr0121112?r2???red(r2)220111?(???1)4ee12?(1?)4e(5分)[74][答案]
?
原式=
?60d??3sec??0f(rcos?,rsin?)rdr???d??26ces?0f(rcos?,rsin?)rdr
(6分)[75][答案]
???rcos??rdrd?D????cos?d??2?22cos?cos?r2dr1???2?cos?(8cos3??cos3?)d? 3?214???2cos4?d?307??8(5分)[76][答案]
原式?1r2sin?cos?rdrd? ??8D41?4
??sin?cos?d??r3dr
080
1?sin2???4?1?
?????r4?8?2??0?4?01144
????0844
(6分)[77][答案]
4
原式???ln(1?r2)rdrd?
D?0??2d??ln(1?r2)rdr0R??R?1???1?r2?ln?1?r2??r2?
22?4??0???1?R2?ln?1?R2??R2??(5分)[78][答案]
原式???sinr?rdrd?
D???d??202rsinrdr2121 ??2?[?rcosr]??cosrdr?1
??2(cos1?2cos2?sin2?sin1)ij,y? (i,j=0,1,2,…,n－1,n)把矩形D：0≤x≤1,0≤y≤1分割成一系列小正方nn用直线x?形，则二重积分
n??xydxdy
Dii1(A)lim???2;n??i?1nnn(C)lim?n??i?1n(B)lim?n??j?1nnij1??2;?i?1nnnni?1i1??2;nnnii11(C)lim?n(?)?.n??nnnni?1
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