# Linear-Algebra-MIT-Gilbert-Strang-(L18-L20)

# Lecture 18. Determinant.

- Det(A), |A|,
**determinant has signs +,-.** - Invertibility. Det(A) > 0 , invertible.
- Sometimes, determinant feels like the area.
**First Property: Det(I) = 1****Second Property: Row exchanging reverse the sign of the determinant.**- A permutation matrix is a row exchanging of I. So the determinant of Permutation matrices is +-1.
- How to compute in 2D