# Definition questions for linear algebra

1. Apr 11, 2012

### futeca

i am having trouble understanding some of the "basic" concepts of my linear algebra...any help would be greatly appreciated

what is an orthogonal basis? and how to construct it? i keep stumbling upon questions asking about construction a orthogonal basis for {v1, v2} in W

what i null A? need to understand the concept fro proofs

what is Col A? also need to understand for proofs

what exactly is a projection? i know the formula for it and i know how to apply it yet i dont understand the concept of what it is or how to picture it

thank you

2. Apr 11, 2012

### DonAntonio

Best advice ever: get yourself a good linear algebra book...:)

Null A = most probably it means the null (sub)space of a matrix (or linear transformation) A, and it is the set of all vectors that A maps to the zero vector

Col A = probably it means the space spanned by the columns of an n x m matrix in the vector space $\mathbb F^n$

DonAntonio

3. Apr 13, 2012

### futeca

thank you so much this is great help!

btw do u happen to have any recommendations for a good linear algebra book to buy?

4. Apr 13, 2012