1
NDA 2017 Paper 1
MCQ (Single Correct Answer)
+2.5
-0.83
Let x, y, z be positive real numbers such that x, y, z are in GP and $${\tan ^{ - 1}}x$$, $${\tan ^{ - 1}}y$$ and $${\tan ^{ - 1}}z$$ are in AP. Then which one of the following is correct?
A
x = y = z
B
xz = 1
C
x $$\ne$$ y and y = z
D
x = y and y $$\ne$$ z
2
NDA 2017 Paper 1
MCQ (Single Correct Answer)
+2.5
-0.83
What is the value of $$\cos (2{\cos ^{ - 1}}0.8)$$ ?
A
0.81
B
0.56
C
0.48
D
0.28
3
NDA 2018 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
Consider the following values of x

1. 8

2. $$-$$4

3. $${1 \over 6}$$

4. $$-$$ $${1 \over 4}$$

Which of the above values of x is/are the solution(s) of the equation $${\tan ^{ - 1}}(2x) + {\tan ^{ - 1}}(3x) = {\pi \over 4}$$ ?
A
Only 3
B
2 and 3
C
1 and 4
D
Only 4
4
NDA 2018 Paper 1
MCQ (Single Correct Answer)
+2.5
-0.83
If $$\sin x = {1 \over {\sqrt 5 }}$$, $$\sin y = {1 \over {\sqrt {10} }}$$, where $$0 < x < {\pi \over 2}$$, $$0 < y < {\pi \over 2}$$, then what is (x + y) equal to?
A
$$\pi$$
B
$${\pi \over 2}$$
C
$${\pi \over 4}$$
D
0
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