带参数的非线性方程组
 

有一带参数的非线性方程组，但是解却求不出来为什么？

>> [c,s]=solve('c*x-s*y=z', 's*x+c*y', 'z^2 = x^2 +y^2', 'c^2+s^2=1', 'c', 's')

Warning: 4 equations in 2 variables.
> In solve at 113
Warning: Explicit solution could not be found.
> In solve at 140

用四个等式求两个未知量，
过约束问题
减少方程数目或运用优化方法求解最优解