All questions of Engineering Mathematics for Electrical Engineering (EE) Exam

If A is a non–singular matrix and the eigen values of A are 2 , 3 , -3 then the eigen values of A-1 are
  • a)
    2 , 3 , - 3
  • b)
    1/2, 1/3, -1/3
  • c)
    2|A|, 3|A|, -3|A|
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Tanishq Chavan answered
If λ1 ,λ2 ,λ3 ....λare the eigen values of a non–singular matrix A, then A-1 has the eigen values  1/λ1 ,1/λ2 ,1/λ3 ....1/λn Thus eigen values of A-1are 1/2, 1/3, -1/3

The number of linearly independent eigenvectors of 
  • a)
    0    
  • b)
    1    
  • c)
    2    
  • d)
    Infinit e 
Correct answer is 'B'. Can you explain this answer?

Pranjal Sen answered
Number of linear independent vectors is equal to the sum of Geometric Multiplicity of eigen values. Here only eigen value is 2. To find Geometric multiplicity find n-r of (matrix-2I), where n is order and r is rank. Rank of obtained matrix is 1 and n=2 so n-r=1. Therefore the no of linearly independent eigen vectors is 1

The eigenvalues of
  • a)
    -19,5,37
  • b)
    19,-5,-37
  • c)
    2,-3,7
  • d)
    3,-5,37
Correct answer is option 'A'. Can you explain this answer?

Avinash Sharma answered
The eigenvalues of an upper triangular matrix are simply the diagonal entries of the matrix.
Hence 5, -19, and 37 are the eigenvalues of the matrix. Alternately, look atd
λ = 5, -19, 37

If -1 , 2 , 3 are the eigen values of a square matrix A then the eigen values of A2 are
  • a)
    -1 , 2 , 3
  • b)
    1, 4, 9
  • c)
    1, 2, 3
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Aditya Patel answered
If λ1 ,λ2 ,λ3 ....λare the eigen values of  a matrix A, then A2 has the eigen values  λ12 ,λ22 ,λ32 ....λn2 So, eigen values of Aare 1, 4, 9.

The CORRECT formula for the sentence, "not all rainy days are cold” is
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'B'. Can you explain this answer?

Sanvi Kapoor answered
 
 
In other words it says ``Some rainy days are not cold" 
Given statement is
¬∀d[R(d)→C(d)]
≡¬∀d[¬R(d)∨C(d)
≡∃d[R(d)∧¬C(d)]

Eigen values of a matrix    are 5 and 1. What are the eigen values of the matrix S2  = SS?
  • a)
    1 and 25  
  • b)
    6 and 4  
  • c)
    5 and 1  
  • d)
    2 and 10 
Correct answer is option 'A'. Can you explain this answer?

EduRev GATE answered
We know If λ be the eigen value of A ⇒λ2 is an eigen value of A2 .
For S matrix, if eigen values are λ1, λ2, λ3,... then for S² matrix, the eigen values will be λ²1 λ²2 λ²3......
For S matrix, if eigen values are 1 and 5 then for S² matrix, the eigen values are 1 and 25

If 1 and 3 are the eigenvalues of a square matrix A then A3 is equal to
  • a)
    13 (A - I2 )
  • b)
    13A - 12 I2
  • c)
    12 (A - I2)
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Pankaj Rane answered
Since 1 and 3 are the eigenvalues of A so the characteristic equation of A is
Also, by Cayley–Hamilton theorem, every square matrix satisfies its own characteristic equation so

If 2 and 4 are the eigen values of A then the eigenvalues of AT are
  • a)
    1/2, 1/4 
  • b)
    2, 4
  • c)
    4, 16
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Sanvi Kapoor answered
The eigenvalues of a matrix A are the roots of the characteristic equation of A, which are invariant under the transpose operation. This means that the matrix A and its transpose AT have the same eigenvalues.
Given that 2 and 4 are the eigenvalues of A, the eigenvalues of AT will also be 2 and 4.

In an M × N matrix such that all non-zero entries are covered in a rows and b column. Then the maximum number of non-zero entries, such that no two are on the same row or column, is 
  • a)
    ≤ a + b    
  • b)
    ≤ max (a, b)  
  • c)
    ≤ min[ M –a, N–b]    
  • d)
    ≤ min  {a, b} 
Correct answer is option 'D'. Can you explain this answer?

Naroj Boda answered
Suppose a < b, for example let a = 3, b= 5, then we can put non-zero entries only in 3 rows and 5 columns. So suppose we put non-zero entries in any 3 rows in 3 different columns. Now we can’t put any other non-zero entry anywhere in matrix, because if we put it in some other row, then we will have 4 rows containing non-zeros, if we put it in one of those 3 rows, then we will have more than one non-zero entry in one row, which is not allowed.
So we can fill only “a” non-zero entries if a < b, similarly if b < a, we can put only “b” non-zero entries. So answer is ≤min(a,b), because whatever is less between a and b, we can put atmost that many non-zero entries.

If the rank of a (5×6) matrix Q is 4, then which one of the following statements is correct?  
  • a)
    Q will have four linearly independent rows and four linearly independent columns  
  • b)
    Q will have four lineally independent rows and five lineally independent columns
  • c)
    QQT will be invertible
  • d)
    QTQ will be invertible 
Correct answer is option 'A'. Can you explain this answer?

Given that rank Q is 4, so it will have 4 linearly independent columns as well as 4 linearly independent rows (∵ row rank of a matrix = column rank of a matrix)

So, A is correct and accordingly B is false.

C is false as order of QQ^T will be 5 x 5 and given that rank of Q is 4 i.e. < 5. So the matrix is QQ^T will be singular and hence not invertible.

Similarly D is false as order of Q^T Q will be 6 x 6 and the matrix is Q^T Q will be singular and hence not invertible.

The sum of the eigenvalues of    is equal to 
  • a)
    18
  • b)
    15
  • c)
    10 
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

Zoya Sharma answered
  • Since the sum of the eigenvalues of an n–square matrix is equal to the trace of the matrix (i.e. sum of the diagonal elements)
  • So, required sum = 8 + 5 + 5  = 18

The number of linearly independent eigenvectors of 
  • a)
    0    
  • b)
    1    
  • c)
    2    
  • d)
    Infinit e 
Correct answer is option 'B'. Can you explain this answer?

Ravi Singh answered
Number of linear independent vectors is equal to the sum of Geometric Multiplicity of eigen values. Here only eigen value is 2. To find Geometric multiplicity find n-r of (matrix-2I), where n is order and r is rank. Rank of obtained matrix is 1 and n=2 so n-r=1. Therefore the no of linearly independent eigen vectors is 1

Find the Eigenvalues of matrix
  • a)
    8, 2
  • b)
    3, -3 
  • c)
    -3, -5 
  • d)
    5, 0
Correct answer is option 'A'. Can you explain this answer?

Sanya Agarwal answered
A - λI = 0
Now, After taking the determinant:
(4 - λ)2 - 1 = 0
16 + λ2 - 8λ - 1 = 0
λ2 - 8λ + 15 = 0
 - 3) (
λ
 - 5) = 0
λ
 = 3, 5

If a square matrix A is real and symmetric, then the eigenvaluesn 
  • a)
    Are always real    
  • b)
    Are always real and positive
  • c)
    Are always real and non-negative
  • d)
    Occur in complex conjugate pairs 
Correct answer is option 'A'. Can you explain this answer?

Ishani Basu answered
Real and Symmetric Square Matrix

A square matrix is a matrix with an equal number of rows and columns. In this case, we are considering a real and symmetric square matrix. A real matrix is a matrix that consists of real numbers as its elements, while a symmetric matrix is a matrix that is equal to its transpose.

Eigenvalues of a Matrix

Eigenvalues are a special set of scalars associated with a linear system of equations represented by a matrix. In other words, they are values that satisfy the equation Av = λv, where A is the matrix, λ is the eigenvalue, and v is the eigenvector.

Properties of Real and Symmetric Square Matrix

Real and symmetric square matrices have some specific properties that help determine the nature of their eigenvalues. These properties are:

1. Real Eigenvalues: Eigenvalues of a real matrix are always real numbers. This means that they do not have any imaginary components. Therefore, option 'a' is correct.

2. Orthogonal Eigenvectors: Real and symmetric matrices have orthogonal eigenvectors. Orthogonal vectors are perpendicular to each other, and their dot product is zero. This property helps in diagonalizing the matrix.

3. Diagonalization: Real and symmetric matrices can always be diagonalized. Diagonalization means transforming the matrix into a diagonal matrix by using the eigenvectors as transformation matrices. This process helps in simplifying calculations involving the matrix.

4. Positive Definiteness: Real and symmetric matrices can have positive eigenvalues, negative eigenvalues, or zero eigenvalues depending on their characteristics. However, it is not always true that the eigenvalues are positive. Therefore, option 'b' is incorrect.

5. Complex Conjugate Pairs: Complex conjugate pairs occur in matrices that are not real and symmetric. In the case of real and symmetric matrices, the eigenvalues are always real and do not occur in complex conjugate pairs. Therefore, option 'd' is incorrect.

Conclusion

In conclusion, if a square matrix is real and symmetric, its eigenvalues are always real. This is because real and symmetric matrices have specific properties that guarantee real eigenvalues. These properties include real eigenvalues, orthogonal eigenvectors, diagonalization, and the absence of complex conjugate pairs.

The maximum value of f ( x) = (1 + cos x) sin x is
  • a)
    3
  • b)
    3√3
  • c)
    4
  • d)
    3√3/4
Correct answer is option 'D'. Can you explain this answer?

Radhika Sharma answered
The given function is:
f(x) = (1 - cos(x))sin(x)

To find the maximum value of the function:
We can find the maximum value of the function by finding the critical points and determining whether they are maximum or minimum points.

Finding the critical points:
The critical points occur when the derivative of the function is zero or undefined. Let's find the derivative of the given function.

f'(x) = (1 - cos(x))cos(x) + sin(x)(-sin(x))
= cos(x) - cos^2(x) - sin^2(x)
= cos(x) - (1 - sin^2(x))
= cos(x) - 1 + sin^2(x)
= sin^2(x) + cos(x) - 1

Simplifying the derivative:
To find the critical points, we need to solve the equation f'(x) = 0.

sin^2(x) + cos(x) - 1 = 0

Using the identity sin^2(x) = 1 - cos^2(x):
1 - cos^2(x) + cos(x) - 1 = 0

Simplifying further:
-cos^2(x) + cos(x) = 0

Factoring out cos(x):
cos(x)(-cos(x) + 1) = 0

Setting each factor to zero:
cos(x) = 0 or -cos(x) + 1 = 0

Solving the first equation:
cos(x) = 0
This occurs when x = π/2 or x = 3π/2.

Solving the second equation:
-cos(x) + 1 = 0
cos(x) = 1
This occurs when x = 0 or x = 2π.

Therefore, the critical points are x = π/2, 3π/2, 0, and 2π.

Determining the nature of critical points:
To determine whether the critical points are maximum or minimum points, we can use the second derivative test. Let's find the second derivative of the function.

f''(x) = d/dx (sin^2(x) + cos(x) - 1)
= 2sin(x)cos(x) - sin(x)

Using the identity 2sin(x)cos(x) = sin(2x):
f''(x) = sin(2x) - sin(x)

Simplifying the second derivative:
f''(x) = 2sin(x)cos(x) - sin(x)
= sin(x)(2cos(x) - 1)

Evaluating the second derivative at the critical points:
f''(π/2) = sin(π/2)(2cos(π/2) - 1)
= 1(2(0) - 1)
= -1

f''(3π/2) = sin(3π/2)(2cos(3π/2) - 1)
= -1(2(0) - 1)
= 1

f''(0

Select a suitable figure from the four alternatives that would complete the figure matrix.

  • a)
     
    1
  • b)
     
    2
  • c)
     
    3
  • d)
    4
Correct answer is option 'D'. Can you explain this answer?

Kiran Datta answered
In each row (as well as each column), the third figure is a combination of all the, elements of the first and the second figures

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