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

31.
If \( (0.2)^{x} = 2 \) and \( \log_{10} 2 = 0.3010 \), then what is the value of x to the nearest tenth?
A.
−10
B.
−0.5
C.
−0.4
D.
−0.2
ANSWER :
C. −0.4
32.
The total number of 5-digit numbers that can be composed of distinct digits from 0 to 9 is
A.
45360
B.
30240
C.
27216
D.
15120
ANSWER :
C. 27216
33.
What is the determinant of the matrix \( \begin{bmatrix} x & y & y+z \\ z & x & z+x \\ y & z & x+y \end{bmatrix} \)?
A.
(x − y)(y − z)(z − x)
B.
(x − y)(y − z)
C.
(y − z)(z − x)
D.
\( (z - x)^{2}(x + y + z) \)
ANSWER :
D. \( (z - x)^{2}(x + y + z) \)
34.
If A, B and C are the angles of a triangle and \( \begin{vmatrix} 1 & 1 & 1 \\ 1+\sin A & 1+\sin B & 1+\sin C \\ \sin A+\sin^{2}A & \sin B+\sin^{2}B & \sin C+\sin^{2}C \end{vmatrix} = 0 \), then which one of the following is correct?
A.
The triangle ABC is isosceles
B.
The triangle ABC is equilateral
C.
The triangle ABC is scalene
D.
No conclusion can be drawn with regard to the nature of the triangle
ANSWER :
A. The triangle ABC is isosceles
35.
Consider the following in respect of matrices A and B of same order:
1. \( A^{2} - B^{2} = (A + B)(A - B) \)
2. \( (A - I)(I + A) = O \Leftrightarrow A^{2} = I \)
where I is the identity matrix and O is the null matrix.
Which of the above is/are correct?
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
B. 2 only
36.
What is \( \frac{2\tan\theta}{1 + \tan^{2}\theta} \) equal to?
A.
\( \cos 2\theta \)
B.
\( \tan 2\theta \)
C.
\( \sin 2\theta \)
D.
\( cosec 2\theta \)
ANSWER :
C. \( \sin 2\theta \)
37.
If \( \sec(\theta - \alpha) \), \( \sec\theta \) and \( \sec(\theta + \alpha) \) are in AP, where \( \cos\alpha \neq 1 \), then what is the value of \( \sin^{2}\theta + \cos\alpha \)?
A.
0
B.
1
C.
−1
D.
\( \frac{1}{2} \)
ANSWER :
A. 0
38.
If \( A + B + C = 180^{\circ} \), then what is \( \sin 2A - \sin 2B - \sin 2C \) equal to?
A.
−4 sin A sin B sin C
B.
−4 cos A sin B cos C
C.
−4 cos A cos B sin C
D.
−4 sin A cos B cos C
ANSWER :
D. −4 sin A cos B cos C
39.
A balloon is directly above one end of a bridge. The angle of depression of the other end of the bridge from the balloon is \( 48^{\circ} \). If the height of the balloon above the bridge is 122 m, then what is the length of the bridge?
A.
\( 122 \sin 48^{\circ} \) m
B.
\( 122 \tan 42^{\circ} \) m
C.
\( 122 \cos 48^{\circ} \) m
D.
\( 122 \tan 48^{\circ} \) m
ANSWER :
B. \( 122 \tan 42^{\circ} \) m
40.
A is an angle in the fourth quadrant. It satisfies the trigonometric equation \( 3(3 - \tan^{2}A - \cot A)^{2} = 1 \). Which one of the following is a value of A?
A.
\( 300^{\circ} \)
B.
\( 315^{\circ} \)
C.
\( 330^{\circ} \)
D.
\( 345^{\circ} \)
ANSWER :
A. \( 300^{\circ} \)