How it is possible to find the eigenvalues of a 2*2 matrice without using of eigen function?

2 次查看（过去 30 天）

显示更早的评论

Habib 2016-4-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/279122-how-it-is-possible-to-find-the-eigenvalues-of-a-2-2-matrice-without-using-of-eigen-function

评论： Habib 2016-4-15

采纳的回答： Torsten

在 MATLAB Online 中打开

Hi every one,

I tried to fine eigenvalues of 2*2 A matrix with det(A-landa*I) and my script is follow as:

 clc
 clear all
 syms landa
 a=input('please enter value of a:');
 b=input('please enter value of b:');
 c=input('please enter value of c:');
 d=input('please enter value of d:');
 A=[a b; c d];    I=[1 0;0 1];   B=landa*I; 
 D=det(A-B)

firstly, I defined landa as syms and after finding determinant, with a=1, b=2, c=3 and d=4, the result is 'landa^2 - 5*landa - 2' . (it is a 2 degree polynomial that saved in D)

so my problem is: How I could got the coefficients of this polynomial for finding the landa1 and landa2 as eigenvalues of A matrix?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Torsten 2016-4-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/279122-how-it-is-possible-to-find-the-eigenvalues-of-a-2-2-matrice-without-using-of-eigen-function#answer_218008

在 MATLAB Online 中打开

eigenvalues=solve(D==0,landa);

Best wishes

Torsten.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Torsten 2016-4-15

在 MATLAB Online 中打开

landa(1)=0.5*(a+d)+sqrt((0.5*(a+d))^2-(a*d-b*c));
landa(2)=0.5*(a+d)-sqrt((0.5*(a+d))^2-(a*d-b*c));

Best wishes

Torsten.

Habib 2016-4-15

Dear Torsten,

your answers was very very useful, thanks.

best regards

habib

请先登录，再进行评论。

类别

Sciences Physics Particle & Nuclear Physics

在 Help Center 和 File Exchange 中查找有关 Particle & Nuclear Physics 的更多信息

Community Treasure Hunt

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

Start Hunting!

Translated by