MATLAB: How can I find the values of t2 t3 in the system of matrices

finite elementmatrixunknownvariable

how to find t2, t3 ?

Best Answer

Just rearraign a little:

b=[1.228 .8655 0;.8655 2.457 .8655;0 .8655 1.228]*[85;18.534;26.371]+[.23561;.47122;.23561]-[1.7374;.36603;0]*85;
A=[.36603 0;3.4747 .36603;.36603 1.7374];
x=A\b;

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MATLAB: How would i solve for t2 and t3 in the last matrix? ive never dealt with variables in matrices before.

Sorry. But no solution exists. You have 4 equations, in only two unknowns.

l1 = .1; %m


l2 = .06; %m
l3 = .08; %m
k1 = 5 ; %W/m*C


k2 = .8 ; %W/m*C
k3 = 15 ; %W/m*C
K1 = (k1/l1) * [1 -1 ; -1 1] %W/C


K2 = (k2/l2) * [1 -1 ; -1 1] %W/C
K3 = (k3/l3) * [1 -1 ; -1 1] %W/C
kg = [ K1(1,1) K1(1,2) 0 0 ;
    K1(2,1) (K1(2,2)+K2(1,1)) K2(1,2) 0 ;
    0 K2(2,1) (K2(2,2)+K3(1,1)) K3(1,2);
    0 0 K3(2,1) K3(2,2)]
f = [ 0;0;0;0]
syms t2 t3
t= [500 ; t2 ; t3 ; 100 ]

Now, look at kg*t.

kg*t
ans =
                   25000 - 50*t2
  (190*t2)/3 - (40*t3)/3 - 25000
 (1205*t3)/6 - (40*t2)/3 - 18750
              18750 - (375*t3)/2

Each of those result must be equal to 0. So 4 equations. But only two unknowns: t2 and t3.

No solution exists.

t23 = solve(f == kg*t)
t23 = 
  struct with fields:
    t2: [0×1 sym]
    t3: [0×1 sym]

As you can see, MATLAB tells us no solution exists. t2 and t3 are empty.

MATLAB: A line of the code is T4=(T3.*T1)./T2 where T2 is a 1×10 double matrix and T3 is a 1x6double matrix. How to reshape one of the matrices so that the line of code works enabling me to get values of T4. T1 is a 1×1 double.

E.g., to get all combinations of the elements:

AT4 = bsxfun(@rdivide,AT3.*T1,T2A(:));

Or in R2016b or later

AT4 = AT3.*T1 ./ T2A(:);

Best Answer

Related Solutions

MATLAB: How would i solve for t2 and t3 in the last matrix? ive never dealt with variables in matrices before.

MATLAB: A line of the code is T4=(T3.*T1)./T2 where T2 is a 1×10 double matrix and T3 is a 1x6double matrix. How to reshape one of the matrices so that the line of code works enabling me to get values of T4. T1 is a 1×1 double.

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