1. More about Matrices
Chapter 4, Sections 5, 7

2. Matrix Determinants
A determinant is a real number associated with a matrix.
Only square matrices have a determinant.
The symbol for determinant can be the phrase “det” in front of a matrix variable, det(A); or vertical bars around a matrix, |A|

3. To find the determinant
To find the determinant of a 2x2 matrix, multiply diagonal 1 and subtract the product of diagonal 2.

4. Determinants in the calculator
Enter the matrix
2nd matrix, over to math
Press enter on det(
2nd matrix, press enter on the matrix you need, enter again

5. Identity Matrix
An identity matrix is a square matrix that has 1’s along the main diagonal and 0’s everywhere else.
When you multiply a matrix by the identity, you get the original matrix back: AI=A=IA

6. Inverse Matrices Not all matrices have an inverse.
When you multiply a matrix and its inverse, you get the identity matrix: A*A-1=I=A-1*A
Not all matrices have an inverse.
To find the inverse of a 2x2 matrix, first find the determinant.
If the determinant=0, the inverse does not exist!!
Inverse matrices can be found on the calculator.

7. Homework Page 23, odd numbers Page 25, all numbers EXIT SLIP:
Explain how identity matrices are similar to multiplying by 1 and how inverse matrices are similar to reciprocals.