Notation in Hoffman and Kunze's Linear Algebra

[Jolb]

I'm in a class that uses Hoffman and Kunze's Linear Algebra, and I've been assigned a problem where I can't figure out their notation.

The notation is A(i,j). A is a matrix. What does this mean?

It doesn't mean the i,j entry in A [that's A with subscripts i,j] and it's not the matrix A with row i and column j removed [that's A(i|j)].

Could somebody tell me what A(i,j) means?

 

[fzero]

There's a discussion (eq 2-18 in the version I have) where they use the notation R(i,j) for the ij'th entry of a matrix. I think they did it to make a subscript on an index more readable. If there's still a confusion you might want to explain the context in which they're using that notation and/or a page reference.

 

[Jolb]

The book I'm using is 2nd edition.

The problem is on p. 149 and the other place I've spotted it is on p. 142. Neither place has a definition...Edit:

I see your reference (p.56). Thanks for your help!

 

[fzero]

It looks like

$$A(j_1,k_1) = A_{j_1k_1}$$

and they decided to use that notation because the double subscripts on the RHS are small and hard to read.