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# Linear Algebra Done Right

Aug 24, 2020
Linear Algebra in math

##### Contents
• Finite v/s Infinite Vector Spaces
• Questions
• Fun

Not many books intended for math majors are accessible to everyone. The book Linear Algebra Done Right by Sheldon Axler is, however, delightfully comfortable to read. I am not sure why everyone recommends this as a second course in linear algebra. In hindsight, I feel like this could have been my first linear algebra book but perhaps I have recency bias.

## Finite v/s Infinite Vector Spaces

Infinite-dimensional spaces have always seemed mysterious but there aren't many special things about them other than some rules from finite-dimensional spaces which break. Here's a few.

• In general, neither injectivity nor surjectivity alone imply invertibility of linear maps. For finite-dimensional vector spaces, however, one is enough.

• Only operators on finite complex vector spaces guarantee existence of eigenvalues. See 5.A.18 for an example.

## Questions

Here is a list of few questions that I found interesting.

• 2.A: 16, 17
• 2.C: 9
• 3.A: 7, 10, 13, 14
• 3.B: 22, 23, 29
• 5.A: 14, 18, 29
• 5.B: 3,4

## Fun

The book has a page numbered $100\sqrt{2}$.