If there are two matrices: A and B where

......0 x 0.............. 2 1 1

A = x 0 0....and B =1 2 1

......0 0 0...............1 1 2

 

if the result of A*B is C:

......1 [math]\sqrt{2}[/math] 1

C = [math]\sqrt{2}[/math] 1 1

......0 0 0

 

I tried many ways to figure out what the x is without success. Any one can help? Thank you.

Did you try writing out the multiplication and making a series of equations?

Is "star" * just matrix multiplication?

 

If so I can't seem to solve it. Are you sure you have the entries of the matrices right?

 

[math] A.B = \left(

\begin{array}{ccc}

x & 2x & x\\

2x & x & x \\

0 & 0 & 0 \\

\end{array}

\right)

[/math]

Edited September 5, 200817 yr by ajb

Also, if you use [ code][ /code] tags (without the space),

then your text will be easier to form into shapes, 
because all the letters are the same size

Thank you for the replys. I currently have a piece of someone else's work, which is doing the matrix multiplication by hand, for example, assuming we have a matrix element A(i,j) (i>j) of matrix A(n,n), to do a matrix multiplication with B(n,n) using a loop, we can have:

 

      Do m=1,j-1
        C(i,m)=C(i,m)+A(i,j)[math]\times[/math]B(i,m)
     EndDo
     Do m=j+1,i-1
        C(i,m)=C(i,m)+A(i,j)[math]\times[/math]B(i,m)
     End do
     Do m=i+1,n
        C(i,m)=C(i,m)+A(i,j)[math]\times[/math]B(i,m)
     End do
        C(i,j)=C(i,j)+[math]\sqrt{2}[/math]A(i,j)[math]\times[/math]B(i,j)
        C(i,i)=C(i,i)+[math]\sqrt{2}[/math]A(i,j)[math]\times[/math]B(i,i)

 

Now I have to make this happen by using a matrix multiplication subroutine. It is a bit difficult to make the compute the matrix elements. I thought it should be like the case of what I wrote in my previous post. Thank you.