用第二类曲面积分求xdydz+ydzdx+zdxdy
问题描述:
用第二类曲面积分求xdydz+ydzdx+zdxdy
积分曲面为球面x^2+Y^2+Z^2=A^2的外侧
答
xdydz+ydzdx+zdxdy
=3×2∫∫zdxdy
=6∫∫ 根号下(A²-x²-y²)dxdy
=6∫2π 0∫A,0 根号下(A²-r²)rdr
=4πA³