利用高斯公式计算曲面积分,∫∫(∑)x^2dydz+y^2dzdx+z^2dxdy,其中∑为平面x=0,y=0,z=0,x+y+z=1 (a>0) 所围立体全表面的外侧.
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åå¼=â«â«â«(Ω)(2x+2y+2z)dxdydz
=2â«(0â1)dxâ«(0â1-x)dyâ«(0â1-x-y)(x+y+z)dz
=â«(0â1)dxâ«(0â1-x)[1-(x+y)²]dy
=â«(0â1)(2/3-x+1/3x³)dx
=1/4