NDA & NA Exam (II)- 2021 - Mathematics Defence Question Paper

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NDA & NA Exam (II)- 2021 - Mathematics

NDA & NA Exam (II)- 2021 - Mathematics Defence Questions

31.
What is the value of the following?
\( \cot\left[\sin^{-1}\frac{3}{5} + \cot^{-1}\frac{3}{2}\right] \)
A.
\( \frac{6}{17} \)
B.
\( \frac{7}{16} \)
C.
\( \frac{16}{7} \)
D.
\( \frac{17}{6} \)
ANSWER :
A. \( \frac{6}{17} \)
32.
Let \( 4 \sin^{2} x = 3 \), where \( 0 < x < \pi \). What is \( \tan 3x \) equal to?
A.
−2
B.
−1
C.
0
D.
1
ANSWER :
C. 0
33.
Let \( p, q \) and 3 be respectively the first, third and fifth terms of an AP. Let \( d \) be the common difference. If the product \( (pq) \) is minimum, then what is the value of \( d \)?
A.
1
B.
\( \frac{3}{8} \)
C.
\( \frac{9}{8} \)
D.
\( \frac{9}{4} \)
ANSWER :
C. \( \frac{9}{8} \)
34.
Consider the following statements in respect of the roots of the equation \( x^{3} - 8 = 0 \):
1. The roots are non-collinear.
2. The roots lie on a circle of unit radius.
Which of the above statements is/are correct?
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
A. 1 only
35.
Let the equation \( \sec x - cosec x = p \) have a solution, where \( p \) is a positive real number. What should be the smallest value of \( p \)?
A.
\( \frac{1}{2} \)
B.
1
C.
2
D.
Minimum does not exist
ANSWER :
D. Minimum does not exist
36.
For what value of \( \theta \), where \( 0 < \theta < \frac{\pi}{2} \), does \( \sin \theta + \sin \theta \cos \theta \) attain maximum value?
A.
\( \frac{\pi}{2} \)
B.
\( \frac{\pi}{3} \)
C.
\( \frac{\pi}{4} \)
D.
\( \frac{\pi}{6} \)
ANSWER :
B. \( \frac{\pi}{3} \)
37.
Consider the following statements in respect of sets:
1. The union over intersection of sets is distributive.
2. The complement of union of two sets is equal to intersection of their complements.
3. If the difference of two sets is equal to empty set, then the two sets must be equal.
Which of the above statements are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
A. 1 and 2 only
38.
Consider three sets \( X, Y \) and \( Z \) having 6, 5 and 4 elements respectively. All these 15 elements are distinct. Let \( S = (X - Y) \cup Z \). How many proper subsets does \( S \) have?
A.
255
B.
256
C.
1023
D.
1024
ANSWER :
C. 1023
39.
Consider the following statements in respect of relations and functions:
1. All relations are functions but all functions are not relations.
2. A relation from \( A \) to \( B \) is a subset of Cartesian product \( A \times B \).
3. A relation in \( A \) is a subset of Cartesian product \( A \times A \).
Which of the above statements are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
B. 2 and 3 only
40.
If \( \log_{10} 2 \log_{2} 10 + \log_{10}(10^{x}) = 2 \), then what is the value of \( x \)?
A.
0
B.
1
C.
\( \log_{2} 10 \)
D.
\( \log_{5} 2 \)
ANSWER :
B. 1