æ±ä¸é¢æ²é¢æå´æçå ä½ä½çä½ç§¯ï¼x+y+z=3ï¼x²+y²+z²=1ï¼x=0ï¼y=0ï¼z=0.
解ï¼è¿æ¯å¨ç¬¬ä¸å¦éå ï¼å¨ä¸ä¸ªæ£±é¿ä¸º3çåé¢ä½å ï¼æå»ä¸ä¸ªçå¿å¨åç¹ï¼åå¾ä¸º1ç(1/8)çç
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V=â«â«â«dxdydz-â«â«â«r²sinÏdÏdθ
=ã0ï¼3ãâ« dxã0ï¼3-xãâ« dyã0ï¼3-x-yãâ«dz -ãÏ/2ï¼0ãâ« sinÏdÏã0ï¼Ï/2ãâ«dθã0ï¼1ã â« r²dr
=ã0ï¼3ãâ« dxã0ï¼3-xãâ«(3-x-y)dy-(1/3)-ãÏ/2ï¼0ãâ« sinÏdÏã0ï¼Ï/2ã(1/3)â«dθ
=ã0ï¼3ãâ«dx(3y-xy-y²/2)ã0ï¼3-xã-ãÏ/2ï¼0ã(Ï/6)â«sinÏdÏ
=ã0ï¼3ãâ«[3(3-x)-x(3-x)-(3-x)²/2]dx-(Ï/6)cosÏãÏ/2ï¼0ã
=ã0ï¼3ãâ«[9-3x-3x+x²-(1/2)(9-6x+x²)]dx
=ã0ï¼3ãâ«[9/2-3x+x²/2)]dx-(Ï/6)=[(9/2)x-3x²/2+x³/6]ã0ï¼3ã-(Ï/6)
=27/2-27/2+27/6-Ï/6=9/2-Ï/6