# DIsplaying the product of matrix operations

I am struggling to find out the option that show the final result of a matrix operations and not the necessary steps to achieve the result.

The last line of the following picture demonstrates the problem, I just want the results

The code:

k1 = 1600;
k2 = 600;
k3 = 3200;
m1 = 1;
m2 = 2;
(*Matriz de rigidez*)
K2 = {{+k1 + k2, -k2}, {-k2, k2 + k3}}
(*Matriz de massa*)
M2 = {{m1, 0}, {0, m2}}
w1 = 40;
w2 = 50;
xi1 = 0.1;
xi2 = 0.1;
A = Inverse[{{1/w1, w1}, {1/w2, w2}}].{{2 xi1}, {2 xi2}}
C2 = A[[1]]*M2 + A[[2]]*K2

• post your codes instead of only a picture. – cvgmt Oct 13 '20 at 3:03
• @cvgmt There it is – Victor Verga Oct 13 '20 at 3:06
• What is your desired outcome? Seems that you can avoid all of the errors that are thrown (& get an understandable result) by just taking again the first Part of each portion of A. That is, using A[[1, 1]] and A[[2, 1]]. This is because you are trying to multiply a matrix by a length 1 list, and to instead have it be the scalar value, you need to again take the first Part of the list to effectively remove the curly brackets around the scalar value. – CA Trevillian Oct 13 '20 at 3:15
• Hi Trevillian, my desired outcome is a single matrix with single elements in each position – Victor Verga Oct 13 '20 at 3:17
• A = Inverse[{{1/w1, w1}, {1/w2, w2}}].{2 xi1, 2 xi2}; That is replace {{2 xi1}, {2 xi2}} by {2 xi1, 2 xi2} – cvgmt Oct 13 '20 at 3:29

Clear["Global*"]

k1 = 1600;
k2 = 600;
k3 = 3200;
m1 = 1;
m2 = 2;
(*Matriz de rigidez*)
K2 = {{+k1 + k2, -k2}, {-k2, k2 + k3}};
(*Matriz de massa*)
M2 = {{m1, 0}, {0, m2}};
w1 = 40;
w2 = 50;
xi1 = 1/10;
xi2 = 1/10;


Modifying the definition of A to result in a vector

A = Inverse[{{1/w1, w1}, {1/w2, w2}}].{2 xi1, 2 xi2};

(C2 = A.{M2, K2}) // MatrixForm


C2 // N // MatrixForm
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