MATLAB Answers

## Multiplication between 2 matrix

Asked by Danilo Teran

### Danilo Teran (view profile)

on 6 Nov 2017
Latest activity Edited by Danilo Teran

### Danilo Teran (view profile)

on 6 Nov 2017
Accepted Answer by Mischa Kim

### Mischa Kim (view profile)

Hi, I need to multiply one matrix, which only number has A = [1 0; 2 3] with a matrix(array) with variables, which are not define yet, but they are numbers, which are not yet defined B = [a b; c d]
I need to get one general solution in order to change a,b,c,d values
Thanks in advance

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## 2 Answers

Answer by Mischa Kim

### Mischa Kim (view profile)

on 6 Nov 2017
Edited by Mischa Kim

### Mischa Kim (view profile)

on 6 Nov 2017
Accepted Answer

Danilo, use the Symbolic Math Toolbox
syms B C a b c d
A = [1 0; 2 3];
B = [a b; c d];
C = A*B
C =
[ a, b]
[ 2*a + 3*c, 2*b + 3*d]

Danilo Teran

### Danilo Teran (view profile)

on 6 Nov 2017
Hi Mischa,
I get it, but as you can see there ist not a mtrix there. In my example I need to do this syms S1 A1 S2 A2 K2 A B C Ss K12 TR AR BR CRT TER1 e BN AII BI CIT A=[-K12/A1 K12/A1 ; K12/A2 -(K12+K2)/A2] B=[S1/A1 0; 0 S2/A2] C=[1 0; 0 K2]
Ss=[B A*B]
STR=[0 1]*inv(Ss)
TR=inv([STR;STR*A])
% TR1=inv([STR;STR*A])
AR=inv(TR)*A*TR
BR=inv(TR)*B
CRT=C*TR
TRE1=[C C*inv(A);STR STR*A]
TE=inv(TRE1)
AE=TRE1*A*TE
BE=TRE1*B
CET=C*TE
zer=tzero(A,B,C,0);
e=C*A*TE
BN=[0 1/CRT(2)]
AII=AE(1,1)
BI=[0 CRT(2)]
CIT=[1 0]
CTN=(1/BN(2))*e
ANN=AE(2,2)
My number values will be S1 S2 A1 A2 K12
But I am getting a problem
Error in Matrixconletras (line 9) STR=[0 1]*inv(Ss)

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Answer by Jan

### Jan (view profile)

on 6 Nov 2017

Or perhaps:
C = [a, b; ...
2*a + 3*c, 2*b + 3*d];

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