NDA & NA Exam (II)- 2018 - Mathematics Defence Question Paper

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NDA & NA Exam (II)- 2018 - Mathematics

NDA & NA Exam (II)- 2018 - Mathematics Defence Questions

41.
The top of a hill observed from the top and bottom of a building of height h is at angles of elevation \( \frac{\pi}{6} \) and \( \frac{\pi}{3} \) respectively. What is the height of the hill?
A.
2h
B.
\( \frac{3h}{2} \)
C.
h
D.
\( \frac{h}{2} \)
ANSWER :
B. \( \frac{3h}{2} \)
42.
What is/are the solution(s) of the trigonometric equation \( cosec x + \cot x = \sqrt{3} \), where \( 0 < x < 2\pi \)?
A.
\( \frac{5\pi}{3} \) only
B.
\( \frac{\pi}{3} \) only
C.
\( \pi \) only
D.
\( \pi, \frac{\pi}{3}, \frac{5\pi}{3} \) only
ANSWER :
B. \( \frac{\pi}{3} \) only
43.
If \( \theta = \frac{\pi}{8} \), then what is the value of \( (2\cos\theta + 1)^{10}(2\cos 2\theta - 1)^{10}(2\cos\theta - 1)^{10}(2\cos 4\theta - 1)^{10} \)?
A.
0
B.
1
C.
2
D.
4
ANSWER :
B. 1
44.
If \( \cos\alpha \) and \( \cos\beta \) \( (0 < \alpha < \beta < \pi) \) are the roots of the quadratic equation \( 4x^{2} - 3 = 0 \), then what is the value of \( \sec\alpha \times \sec\beta \)?
A.
\( -\frac{4}{3} \)
B.
\( \frac{4}{3} \)
C.
\( \frac{3}{4} \)
D.
\( -\frac{3}{4} \)
ANSWER :
A. \( -\frac{4}{3} \)
45.
Consider the following values of x:
1. 8
2. −4
3. \( \frac{1}{6} \)
4. \( -\frac{1}{4} \)
Which of the above values of x is/are the solution(s) of the equation \( \tan^{-1}(2x) + \tan^{-1}(3x) = \frac{\pi}{4} \)?
A.
3 only
B.
2 and 3 only
C.
1 and 4 only
D.
4 only
ANSWER :
A. 3 only
46.
If the second term of a GP is 2 and the sum of its infinite terms is 8, then the GP is
A.
\( 8, 2, \frac{1}{2}, \frac{1}{8}, \ldots \)
B.
\( 10, 2, \frac{2}{5}, \frac{2}{25}, \ldots \)
C.
\( 4, 2, 1, \frac{1}{2}, \frac{1}{4}, \ldots \)
D.
\( 6, 3, \frac{3}{2}, \frac{3}{4}, \ldots \)
ANSWER :
C. \( 4, 2, 1, \frac{1}{2}, \frac{1}{4}, \ldots \)
47.
If a, b, c are in AP or GP or HP, then \( \frac{a - b}{b - c} \) is equal to
A.
\( \frac{b}{a} \) or 1 or \( \frac{b}{c} \)
B.
\( \frac{c}{a} \) or \( \frac{c}{b} \) or 1
C.
1 or \( \frac{a}{b} \) or \( \frac{a}{c} \)
D.
1 or \( \frac{a}{b} \) or \( \frac{c}{a} \)
ANSWER :
C. 1 or \( \frac{a}{b} \) or \( \frac{a}{c} \)
48.
What is the sum of all three-digit numbers that can be formed using all the digits 3, 4 and 5, when repetition of digits is not allowed?
A.
2664
B.
3882
C.
4044
D.
4444
ANSWER :
A. 2664
49.
The ratio of roots of the equations \( ax^{2} + bx + c = 0 \) and \( px^{2} + qx + r = 0 \) are equal. If \( D_{1} \) and \( D_{2} \) are respective discriminants, then what is \( \frac{D_{1}}{D_{2}} \) equal to?
A.
\( \frac{a^{2}}{p^{2}} \)
B.
\( \frac{b^{2}}{q^{2}} \)
C.
\( \frac{c^{2}}{r^{2}} \)
D.
None of the above
ANSWER :
B. \( \frac{b^{2}}{q^{2}} \)
50.
If \( A = \sin^{2}\theta + \cos^{4}\theta \), then for all real \( \theta \), which one of the following is correct?
A.
\( 1 \leq A \leq 2 \)
B.
\( \frac{3}{4} \leq A \leq 1 \)
C.
\( \frac{13}{16} \leq A \leq 1 \)
D.
\( \frac{3}{4} \leq A \leq \frac{13}{16} \)
ANSWER :
B. \( \frac{3}{4} \leq A \leq 1 \)