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Level 1 Worksheet: Determinants
Student Name: ____________________________________ Class: 12 Subject: Mathematics
Topic 1: Evaluation of Determinants
1.
Evaluate the determinant: $\Delta = \begin{vmatrix} 4 & 5 \\ -2 & 3 \end{vmatrix}$.
2.
Find the value of $\begin{vmatrix} \cos 60^\circ & \sin 60^\circ \\ -\sin 60^\circ & \cos 60^\circ \end{vmatrix}$.
3.
If $\begin{vmatrix} 2x & 5 \\ 8 & x \end{vmatrix} = \begin{vmatrix} 6 & 5 \\ 8 & 3 \end{vmatrix}$, find the value(s) of $x$.
4.
Evaluate: $\begin{vmatrix} a+b & a \\ b & a-b \end{vmatrix}$.
5.
Evaluate the determinant: $\Delta = \begin{vmatrix} 3 & -1 & -2 \\ 0 & 0 & -1 \\ 3 & -5 & 0 \end{vmatrix}$. (Hint: Expand along a row/column with maximum zeros).
6.
Find the determinant of matrix $A = \begin{bmatrix} 1 & 2 & 4 \\ -1 & 3 & 0 \\ 4 & 1 & 0 \end{bmatrix}$.
7.
If $A = \begin{bmatrix} 1 & 1 \\ -2 & 3 \end{bmatrix}$, find $|2A|$.
8.
Solve for $x$: $\begin{vmatrix} x-2 & -3 \\ 3x & 2x \end{vmatrix} = 3$.
9.
What is the determinant of a $3 \times 3$ upper triangular matrix where the diagonal elements are $2, -3,$ and $5$?
10.
If $\Delta = \begin{vmatrix} 0 & a \\ -a & 0 \end{vmatrix}$, find the value of $\Delta$.
Topic 2: Properties of Determinants
11.
Without expanding, evaluate: $\begin{vmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 1 & 2 & 3 \end{vmatrix}$.
12.
If $\begin{vmatrix} a & b & c \\ d & e & f \\ g & h & i \end{vmatrix} = 10$, find the value of $\begin{vmatrix} a & b & c \\ g & h & i \\ d & e & f \end{vmatrix}$.
13.
If $A$ is a square matrix of order 3 and $|A| = 7$, find the value of $|3A|$.
14.
Without expanding, show that $\begin{vmatrix} 2 & 7 & 65 \\ 3 & 8 & 75 \\ 5 & 9 & 86 \end{vmatrix} = 0$. (Hint: Apply $C_3 \to C_3 - 9C_2$).
15.
Evaluate without expanding: $\begin{vmatrix} x & y & z \\ a & b & c \\ x+a & y+b & z+c \end{vmatrix}$.
16.
Let $A$ be a skew-symmetric matrix of odd order (e.g., $3 \times 3$). What is the value of $|A|$?
17.
Given $|A| = -4$, find the determinant of $A^T$.
18.
Use properties to evaluate $\begin{vmatrix} 102 & 18 & 36 \\ 1 & 3 & 4 \\ 17 & 3 & 6 \end{vmatrix}$.
19.
If we apply the operation $R_1 \to R_1 + 2R_2$ on a determinant $\Delta$, what will be the new value of the determinant?
20.
If every element of a $3 \times 3$ determinant is multiplied by $-1$, how does the value of the determinant change?
Topic 3: Area of a Triangle & Collinearity
21.
Find the area of the triangle with vertices $(2, 7)$, $(1, 1)$, and $(10, 8)$ using determinants.
22.
Find the area of the triangle whose vertices are $(-2, -3)$, $(3, 2)$, and $(-1, -8)$.
23.
Use determinants to show that the points $(a, b+c)$, $(b, c+a)$, and $(c, a+b)$ are collinear.
24.
Find the equation of the line joining $(1, 2)$ and $(3, 6)$ using determinants.
25.
If the points $(2, -3)$, $(k, -1)$, and $(0, 4)$ are collinear, find the value of $k$.
26.
Find the value(s) of $k$ if the area of the triangle is 4 sq. units and vertices are $(k, 0)$, $(4, 0)$, and $(0, 2)$.
27.
Find $k$ if the area of a triangle is $35$ sq. units with vertices $(2, -6)$, $(5, 4)$, and $(k, 4)$.
28.
Can the area of a triangle obtained using the determinant formula be negative? If yes, how do we report the final area?
29.
Find the area of the triangle with vertices $(0, 0)$, $(0, 5)$, and $(4, 0)$.
30.
Using determinants, find the equation of the line joining $(3, 1)$ and $(9, 3)$.
Topic 4: Minors, Cofactors & Adjoint
31.
Find the minor $M_{21}$ and cofactor $A_{21}$ of the element in the matrix $\begin{bmatrix} 1 & -2 \\ 4 & 3 \end{bmatrix}$.
32.
Write the cofactor matrix for $A = \begin{bmatrix} 2 & -1 \\ 3 & 4 \end{bmatrix}$.
33.
Find the adjoint of the matrix $A = \begin{bmatrix} 2 & 3 \\ 1 & 4 \end{bmatrix}$.
34.
For the determinant $\Delta = \begin{vmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{vmatrix}$, find the minor $M_{22}$.
35.
For the determinant in Q34, find the cofactor $A_{23}$.
36.
If $A$ is a square matrix of order 3 and $|A| = 6$, find the value of $|adj(A)|$.
37.
If $A$ is a non-singular matrix of order 2 and $|A| = 4$, find $A \cdot (adj A)$.
38.
Verify that $A(adj A) = |A|I$ for the matrix $A = \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix}$. (Find $|A|$ first).
39.
If the value of a determinant is $\Delta$, what is the sum of the products of elements of any row with their corresponding cofactors?
40.
If $A = \begin{bmatrix} 5 & -2 \\ 3 & -2 \end{bmatrix}$, find $adj(A)$.
Topic 5: Inverse of a Matrix & Solving Systems
41.
Find the inverse of the matrix $A = \begin{bmatrix} 2 & -2 \\ 4 & 3 \end{bmatrix}$.
42.
Determine if the matrix $A = \begin{bmatrix} 6 & 4 \\ 3 & 2 \end{bmatrix}$ is invertible.
43.
If $A = \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}$, find $A^{-1}$.
44.
For what value of $x$ is the matrix $A = \begin{bmatrix} 3 - x & 2 \\ 4 & 1 \end{bmatrix}$ singular?
45.
Write the system of equations $2x + 3y = 5$ and $x - 2y = 4$ in the matrix form $AX = B$.
46.
Check the consistency of the system: $x + 2y = 2$, $2x + 3y = 3$.
47.
Check the consistency of the system: $x + 3y = 5$, $2x + 6y = 8$.
48.
If a system of equations $AX = B$ has $|A| \neq 0$, the system has a _______ solution.
49.
Solve the system $5x + 2y = 4$, $7x + 3y = 5$ using the matrix method.
50.
If $A^{-1} = \begin{bmatrix} 3 & -1 \\ -5/2 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} 1 \\ 2 \end{bmatrix}$, find the solution matrix $X$.