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Consider the following statements in res...

Consider the following statements in respect of symmetric matrices A and B
1. AB is symmetric.
2. `A^(2) + B^(2)` is symmetric.
Which of the above statement(s) is/are correct ?

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

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The correct Answer is:
To determine the correctness of the statements regarding symmetric matrices A and B, we will analyze each statement step by step. ### Step 1: Analyze the first statement - "AB is symmetric." - A matrix \( M \) is symmetric if \( M^T = M \). - For the product of two matrices \( AB \), we need to check if \( (AB)^T = AB \). - Using the property of transposes, we have: \[ (AB)^T = B^T A^T \] - Since A and B are symmetric, we know that \( A^T = A \) and \( B^T = B \). - Therefore, substituting these into our equation gives us: \[ (AB)^T = B A \] - For \( AB \) to be symmetric, we would need \( B A = AB \). However, this is not generally true for arbitrary matrices A and B. - Hence, the first statement is **incorrect**. ### Step 2: Analyze the second statement - "A² + B² is symmetric." - We need to check if \( A^2 + B^2 \) is symmetric. - A matrix \( M \) is symmetric if \( M^T = M \). - We calculate the transpose of \( A^2 + B^2 \): \[ (A^2 + B^2)^T = A^2 + B^2 \] - Using the property of transposes, we have: \[ (A^2)^T + (B^2)^T \] - Since \( A \) and \( B \) are symmetric, we know that: \[ (A^2)^T = (A^T A^T) = A A = A^2 \] \[ (B^2)^T = (B^T B^T) = B B = B^2 \] - Therefore, we can conclude: \[ (A^2 + B^2)^T = A^2 + B^2 \] - This shows that \( A^2 + B^2 \) is symmetric. - Hence, the second statement is **correct**. ### Conclusion: - The first statement is incorrect, and the second statement is correct. - Therefore, the answer is **Option B: Only statement 2 is correct**.

To determine the correctness of the statements regarding symmetric matrices A and B, we will analyze each statement step by step. ### Step 1: Analyze the first statement - "AB is symmetric." - A matrix \( M \) is symmetric if \( M^T = M \). - For the product of two matrices \( AB \), we need to check if \( (AB)^T = AB \). - Using the property of transposes, we have: \[ (AB)^T = B^T A^T ...
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NDA PREVIOUS YEARS-MATRICES & DETERMINANTS-MQS
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  2. What is the inverse of A=[{:(0,0,1),(0,1,0),(1,0,0):}]?

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  3. Consider the following statements in respect of symmetric matrices A a...

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  4. The following item consists of two statements, one labelled the Assert...

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  6. If a ,b and c are all non-zero and |1+a1 1 1a+b1 1 1a+c|=0, then pr...

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  7. If a matrix A is symmetric as well as anti-symmetric, then which one o...

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  8. If A=[{:(1,-2,-3),(2,1,-2),(3,2,1):}], then which one of the following...

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  9. A=|{:(2a,3r,x),(4b,6s,2y),(-2c,-3t,-z):}|=lambda|{:(a,r,x),(b,s,y),(c,...

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  10. What is the value of |{:(" "1-i," "omega^(2)," "-omega),(" "omega^(2)...

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  11. If A=[{:(omega,0),(0,omega):}], where omega is cube root of unity, the...

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  12. A matrix X has a+b rows and a+2 columns while the matrix Y has b+1 ...

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  13. If |{:(a,b,c),(l,m,n),(p,q,r):}|=2, then what is the value of the dete...

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  14. Let A = [{:(5,6,1),(2,-1,5):}]. Let there exist a matrix B such that A...

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  15. Consider the following statements 1. If A' = A, then A is a singular...

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  16. If the system of equations 2x + 3y = 7 and 2ax + (a + b) y = 28 has in...

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  17. If the lines 3y+4x=1, y=x+5 and 5y+bx=3 are concurrent then b=

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  18. What is the value of |{:(cos 15^(@),sin 15^(@)),(cos 45^(@),sin 45^(@)...

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  19. Let A be an n xx n matrix. If det (lambda A) = lambda^(s) det(A), what...

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  20. If A be a real skew-symmetric matrix of order n such that A^(2)+I=0, I...

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