Home
Class 12
MATHS
Let A be a 2 xx 2 matrix with non-zero e...

Let A be a `2 xx 2` matrix with non-zero entries and let A^2=I, where i is a `2 xx 2` identity matrix, Tr(A) i= sum of diagonal elements of A and `|A|` = determinant of matrix A. Statement 1:Tr(A)=0 Statement 2:`|A|`=1

A

Statement 1 is false, statement 2 is true.

B

Statement 1 is true, statement 2 is true, statement 2 is a correct explanation for statement 1.

C

Statement 1 is true, statement 2 is true, statement 2 is a correct explanation for statement 1.

D

Statement 1 is true, statement 2 is false.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the properties of the matrix \( A \) given that \( A^2 = I \), where \( I \) is the \( 2 \times 2 \) identity matrix. Let \( A \) be represented as: \[ A = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \] ### Step 1: Calculate \( A^2 \) We compute \( A^2 \): \[ A^2 = A \cdot A = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \cdot \begin{pmatrix} a & b \\ c & d \end{pmatrix} = \begin{pmatrix} a^2 + bc & ab + bd \\ ac + dc & bc + d^2 \end{pmatrix} \] ### Step 2: Set \( A^2 \) equal to the identity matrix Since \( A^2 = I \), we have: \[ \begin{pmatrix} a^2 + bc & ab + bd \\ ac + dc & bc + d^2 \end{pmatrix} = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix} \] From this, we can derive the following equations: 1. \( a^2 + bc = 1 \) 2. \( ab + bd = 0 \) 3. \( ac + dc = 0 \) 4. \( bc + d^2 = 1 \) ### Step 3: Analyze the equations From equations 2 and 3, we can factor them: - From \( ab + bd = 0 \), we can factor out \( b \): \( b(a + d) = 0 \) - From \( ac + dc = 0 \), we can factor out \( c \): \( c(a + d) = 0 \) Since \( A \) has non-zero entries, \( b \neq 0 \) and \( c \neq 0 \). Therefore, we must have: \[ a + d = 0 \implies d = -a \] ### Step 4: Substitute \( d \) into the equations Now substituting \( d = -a \) into equations 1 and 4: 1. \( a^2 + bc = 1 \) 2. \( bc + (-a)^2 = 1 \) simplifies to \( bc + a^2 = 1 \) Both equations are the same, confirming our substitution is consistent. ### Step 5: Calculate the trace and determinant The trace \( \text{Tr}(A) \) is given by: \[ \text{Tr}(A) = a + d = a - a = 0 \] The determinant \( |A| \) is calculated as: \[ |A| = ad - bc = a(-a) - bc = -a^2 - bc \] From \( a^2 + bc = 1 \), we can substitute \( bc = 1 - a^2 \): \[ |A| = -a^2 - (1 - a^2) = -a^2 - 1 + a^2 = -1 \] ### Conclusion 1. **Statement 1**: \( \text{Tr}(A) = 0 \) is **true**. 2. **Statement 2**: \( |A| = 1 \) is **false** (we found \( |A| = -1 \)).

To solve the problem, we need to analyze the properties of the matrix \( A \) given that \( A^2 = I \), where \( I \) is the \( 2 \times 2 \) identity matrix. Let \( A \) be represented as: \[ A = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \] ### Step 1: Calculate \( A^2 \) ...
Promotional Banner

Topper's Solved these Questions

  • MATRICES

    CENGAGE ENGLISH|Exercise JEE Advanced (Single Correct Answer Type)|5 Videos
  • MATRICES

    CENGAGE ENGLISH|Exercise Single correct Answer|34 Videos
  • MATRICES

    CENGAGE ENGLISH|Exercise Numerical Value Type|27 Videos
  • MATHMETICAL REASONING

    CENGAGE ENGLISH|Exercise Archives|10 Videos
  • METHODS OF DIFFERENTIATION

    CENGAGE ENGLISH|Exercise Single Correct Answer Type|46 Videos

Similar Questions

Explore conceptually related problems

Let A be a 2xx 2 matrix with real entries and det (A)= 2 . Find the value of det ( Adj(adj(A) )

Let A be a 2xx2 matrix with real entries. Let I be the 2xx2 identity matrix. Denote by tr (A), the sum of diagonal entries of A. Assume that A^2=""I . Statement 1: If A!=I and A!=""-I , then det A""=-1 . Statement 2: If A!=I and A!=""-I , then t r(A)!=0 . (1) Statement 1 is false, Statement ( 2) (3)-2( 4) is true (6) Statement 1 is true, Statement ( 7) (8)-2( 9) (10) is true, Statement ( 11) (12)-2( 13) is a correct explanation for Statement 1 (15) Statement 1 is true, Statement ( 16) (17)-2( 18) (19) is true; Statement ( 20) (21)-2( 22) is not a correct explanation for Statement 1. (24) Statement 1 is true, Statement ( 25) (26)-2( 27) is false.

If M is a 3 xx 3 matrix, where det M=1 and MM^T=1, where I is an identity matrix, prove theat det (M-I)=0.

Let M be a 2xx2 symmetric matrix with integer entries. Then , M is invertible, if

if for a matrix A, A^2+I=O , where I is the identity matrix, then A equals

Let A be any 3xx 2 matrix show that AA is a singular matrix.

Let A and B be two 2 xx 2 matrix with real entries, If AB=0 and such that tr(A)=tr(B)=0then

If A is a diagonal matrix of non-positive entries and order 3 such that A^2=I , then

Let A be 2 x 2 matrix.Statement I adj (adj A) = A Statement II |adj A| = |A|

Let A be a matrix of order 3 such that A^(2)=3A-2I where, I is an identify matrix of order 3. If A^(5)=alphaA+betaI , then alphabeta is equal to