化成参数方程,x=a(cost)^3,y=a(sint)^3,图形星形线第一象限和正方形之间所围成图形,S=∫ [0,a] ydx=4∫ [π/2,0] a(sint)^3d[a (cost)^3]=a^2∫ [π/2,0] (sint)^3 *[3(cost)^2*(-sint)]dt=(-3a^2)∫ [π/2,0](sint)...