设参数方程x=t(1-sint);y=tcost , a为常数, 求二阶导数 d^2y/(dx^2)

dy/dx=(dy/dt)/(dx/dt)=(cost-tsint)/(1-sint-tcost)
d^2y/dx^2=(dy/dx)/(dx/dt)
=[(-sint-sint-tcost)(1-sint-tcost)-(cost-tsint)(-cost-cost+tsint)/(1-sint-tcost)^3
=[(2sint+tcost)(sint+tcost-1)+(cost-tsint)(2cost-tsint)]/(1-sint-tcost)^3
后面的展开计算化简了.