# equation solving with 3 variables and 4 equations

1 vue (au cours des 30 derniers jours)
Caleb Coombe le 1 Juil 2021
Hello,
I am having trouble with my code depending upon the inputs. Here is the code: clc;
clear;
sx=input('sigma_x=');
sy=input('sigma_y=');
sz=input('sigma_z=');
txy=input('tau_xy=');
tyz=input('tau_yz=');
tzx=input('tau_zx=');
A = [sx txy tzx; txy sy tyz; tzx tyz sz];
[V,D] = eig(A);
[d,ind] = sort(diag(D));
s1 = d(3)
s2 = d(2)
s3 = d(1)
syms i1 m1 n1
eq1 = ((sx - s1)*i1) +(txy*m1) + (tzx*n1)==0;
eq2 = (txy*i1) +((sy-s1)*m1) + (tyz*n1)==0;
eq3 = (tzx*i1) + (tyz*m1) + ((sz-s1)*n1)==0;
eq4 = (i1)^2+(m1)^2+(n1)^2==1;
[i1,m1,n1] = solve(eq1,eq2,eq3,eq4,i1,m1,n1);
i1= vpa(i1(1))
m1= vpa(m1(1))
n1= vpa(n1(1))
When sx=50, sy=100, sz=0, txy=-60, tyz=0, and tzx=0 the code works fine and I find my values for i1, m1, and n1.
When sx=-40, sy=100, sz=30, txy=-50, tyz=12 , and tzx =0 the equations (eq1,eq2,eq3) have these crazy values and I do not understand why.
Please let me know if you know how to resolve this issue!! Thank you for your help.
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