# Matrix multiplication

1. Feb 26, 2010

### jugalyash

if A is [A1|A2|A3|...|An] and C is 1 column matrix given by [C1|C2|C3|...|Cn]T then AC=C1A1+C2A2+...+CnAn.. If D is a diagonal matrix then AD = [D11A1+D22A2+...+DNnAn]. please explain why it happens tht way and whts the prof?

2. Feb 26, 2010

### Gib Z

The first rule you state is true but only tells you about the product of vectors. Do you know the definition for the product for $A_{(p,r)}$ and $D_{(r,q)}$? Find the definition in your textbook and give it a try and post us what you did.

This should be in the homework forum!