用二重积分,会的帮个忙呀 答案 ∵z=√(x²+y²)∴z'x=x/√(x²+y²),z'y=y/√(x²+y²) ==>√(1+z'x²+z'y²)=√2∵z=√(x²+y²)被z²=2x所割下部分在xy平面上的投影是圆(x-1)²+y²=1 ∴所求面积=2∫(0,π/2)dθ∫(0,2cosθ)√2rdr (利用...