How to solve a system of equations?

1 次查看（过去 30 天）
Jessie Bessel
Jessie Bessel 2018-2-27
评论： Walter Roberson 2018-3-1
I try to solve a non=linear equtions system, but it doesn't work. I missed something?
F=@(x)[sqrt((x(1)-5)^2 + x(2)^2 + x(3)^2 )-sqrt( x(1)^2 + (x(2)+10)^2 + x(3)^2) +0.34;
sqrt(x(1)^2 + (x(2)+10)^2 + x(3)^2 )-sqrt( x(1)^2 + (x(2)-10)^2 + x(3)^2);
sqrt( x(1)^2 + (x(2)-10)^2 + x(3)^2 )-sqrt( x(1)^2 + x(2)^2 + x(3)^2)];
x0=[50;0;0];
fsolve(F,x0)

请先登录，再回答此问题。

回答（2 个）

Alan Weiss
Alan Weiss 2018-2-27
You have an errant space just before "+0.34" that is confusing the parser. Try this:
F=@(x)[sqrt((x(1)-5)^2 + x(2)^2 + x(3)^2 )-sqrt( x(1)^2 + (x(2)+10)^2 + x(3)^2)+0.34;
sqrt(x(1)^2 + (x(2)+10)^2 + x(3)^2 )-sqrt( x(1)^2 + (x(2)-10)^2 + x(3)^2);
sqrt( x(1)^2 + (x(2)-10)^2 + x(3)^2 )-sqrt( x(1)^2 + x(2)^2 + x(3)^2)];
x0=[50;0;0];
fsolve(F,x0)
You might need to include some options or a better start point for a good answer.
Alan Weiss
MATLAB mathematical toolbox documentation
  2 个评论
Jessie Bessel
Jessie Bessel 2018-2-28
when i do that, the solver tell me that there is no solution found, but what are the value from ans?Originally, there should have been the solutions, but if the system doesn't have solutions, what are they?
Walter Roberson
Walter Roberson 2018-3-1
They are the value of the vector x at the time that fsolve figured out that the system could not be solved.

请先登录，再进行评论。

Roger Stafford
Roger Stafford 2018-2-28
To solve these you would have to satisfy both
x(1)^2 + (x(2)+10)^2 + x(3)^2 = x(1)^2 + (x(2)-10)^2 + x(3)^2
x(1)^2 + (x(2)-10)^2 + x(3)^2 = x(1)^2 + x(2)^2 + x(3)^2)
and since the x(1) and x(3) terms cancel would require simply
(x(2)+10)^2 = (x(2)-10)^2
(x(2)-10)^2 = x(2)^2
The first of these requires that x(2) = 0 while the second requires that x(2) = 5. These are mutually incompatible and therefore there are no simultaneous solutions to your equations. That is why "it doesn't work".
  1 个评论
Jessie Bessel
Jessie Bessel 2018-2-28
when i do that, the solver tell me that there is no solution found, but what are the value from ans?Originally, there should have been the solutions, but if the system doesn't have solutions, what are they?

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Systems of Nonlinear Equations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by