How to get my code for Newtons method for non-linear equationsystems working?

3 次查看（过去 30 天）

Marcus 2014-12-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168184-how-to-get-my-code-for-newtons-method-for-non-linear-equationsystems-working

评论： Marcus 2014-12-26

I'm trying to make my code for Newtons method for non-linear equationsystems working. I have three equations and three variables, u(1), u(2), u(3):

cos(u(1))+cos(u(2))+L3*cos(u(3))-2

sin(u(1))+sin(u(2))+L3*sin(u(3))

m2*tan(u(1))-(m1+m2)*tan(u(2))+m1*tan(u(3))

We have also been given several different values of L3, m1 and m2 to work with and the code should be able to find the solution for these different values. My code looks like this:

function g = uppgift12(L3, m1, m2)
u=[pi/4 pi/4 pi/4]';
iter=0;, dunorm=1;
while dunorm>0.5e-4 & iter<10
 f=[cos(u(1))+cos(u(2))+L3*cos(u(3))-2
    sin(u(1))+sin(u(2))+L3*sin(u(3))
    m2*tan(u(1))-(m1+m2)*tan(u(2))+m1*tan(u(3))];
 J=[-sin(u(1)) -sin(u(2)) -L3*sin(u(3))
    cos(u(1)) cos(u(2)) L3*cos(u(3))
    m2*sec(u(1))^2 -m1*sec(u(2))^2-m2*sec(u(2))^2 m1*sec(u(3))^2];
 du=-J/f;
 u=u+du;
 dunorm=norm(du,inf), iter=iter+1;
end
u, iter

My startguesses is pi/4 for all three variables (that can change if necessary of course). I can't get the code to work however. I'm really bad at coding and I don't know what to do so I would be really grateful for any help I can get.