计算曲面积分∫∫∑√(R2-x2-y2)dS,其中∑为球心在坐标原点,半径为R的上半球面.
∑:=√(R2-x2-y2) ∑在Oxy平面上的投影为D:x2+y2≤R2 ∫∫∑√(R2-x2-y2)dS =∫∫D√(R2-x2-y2)√[1+(∂z/∂x)2+(∂z/∂y)2]dxdy =∫∫D√(R2-x2-y2)•[R/√(R2-x2-y2)]dxdy =∫∫DRdxdy=πR3
计算曲面积分∫∫∑√(R2-x2-y2)dS,其中∑为球心在坐标原点,半径为R的上半球面.
∑:=√(R2-x2-y2) ∑在Oxy平面上的投影为D:x2+y2≤R2 ∫∫∑√(R2-x2-y2)dS =∫∫D√(R2-x2-y2)√[1+(∂z/∂x)2+(∂z/∂y)2]dxdy =∫∫D√(R2-x2-y2)•[R/√(R2-x2-y2)]dxdy =∫∫DRdxdy=πR3