Determinant ●2×2-Diagonal Method Main Diagonala1 21 =110 Secondary Diag 212 Tongji University】 4/32Determinant 2 × 2—Diagonal Method . a11. a12. a21. a22. .        .        . = a11a22 . Main Diagonal −a12a21 . Secondary Diag (Tongji University) Linear Algebra 4 / 32