x²+(y-5)²=16 绕着x轴旋转得到图形的面积y1 = 5+√(16-x²),ds = √(1+y'²) dx = 4dx /√(16-x²)y2 = 5-√(16-x²),ds = √(1+y'²) dx = 4dx /√(16-x²)S = 2π ∫[-4,4] y1 ...