绘制圆柱面x^2+y^2=1,y^2+z^2=1,z^2+x^2=1相交图形 画理论计算出的最速落径（虚线表示） 多元函数求极值法模拟最速降线 二次函数 f(x)=4x(1-x) 的迭代密度分布图 二次函数f(x)=ax(1-x) 迭代蛛网图 -Draw a cylindrical surface x ^ 2+y ^ 2 = 1, y ^ 2+z ^ 2 = 1, z ^ 2+x ^ 2 = 1 intersects graphics　painting theoretical calculation showing the most speed drop diameter (dashed lines said)　multivariate function seeking extreme value method simulation the most speed drop line　the iterative density distribution of the quadratic function f (x) = 4x (1-x)　quadratic function f (x) = ax (1-x) of iterative spider diagram