# I Notation (index notation)

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1. Mar 18, 2016

### kezzstar

I am having trouble converting [D]=[A][ B]T[C] to index notation.
I initially thought it would be Dij=AijBkjCkl but I have doubts that this is correct.

Would anyone be able to elaborate on this?

Regards

2. Mar 18, 2016

### Khashishi

Where did B come from?

3. Mar 18, 2016

### kezzstar

BT? It is the transpose of B.

4. Mar 18, 2016

### Khashishi

Err, did you edit your post? I didn't see a B in your equation before. Anyways, nevermind.

5. Mar 18, 2016

### kezzstar

No I never editted the equation. Do you have any ideas?

6. Mar 18, 2016

### Staff: Mentor

The OP had [B], which browsers treat as the start tag for bold fonts. That screwed up the equation. I edited the equation to fix that problem.

7. Mar 19, 2016

### Svein

OK. Let us start at the right. First: $B^{T}_{j,k}=B_{k,j}$, so $(B^{T}\circ C)_{j,l}=\sum _{k}B^{T}_{j,k}C_{k,l}$. Then inset A at the front in the same way: $A\circ (B^{T}\circ C)_{i,l}=\sum _{j}A_{i,j}(\sum _{k}B^{T}_{j,k}C_{k,l})$.