Cut the paper cup along the generatrix to form an isosceles trapezoid. The area of this trapezoid is the surface area of the paper cup. The upper and lower bottoms of the trapezoid are 8 and 4 respectively. By calculating the height, we can find the vertical line passing through the trapezoidal area of the trapezoidal bottom as the upper bottom. This vertical line is the height of the trapezoid, and the square of the height = 8 2-[(8-4)/2] 2 = 60, so the height = 2 √ 65430.