1
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

If $${\sec ^{ - 1}}\left( {{{1 + x} \over {1 - y}}} \right) = a$$, then $${{dy} \over {dx}}$$ is

A
$${{y + 1} \over {x - 1}}$$
B
$${{y - 1} \over {x + 1}}$$
C
$${{x - 1} \over {y + 1}}$$
D
$${{x - 1} \over {y - 1}}$$
2
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

If $$y = {\cos ^2}{{3x} \over 2} - {\sin ^2}{{3x} \over 2}$$, then $${{{d^2}y} \over {d{x^2}}}$$ is

A
9y
B
$$ - 3\sqrt {1 - {y^2}} $$
C
$$3\sqrt {1 - {y^2}} $$
D
$$ - 9y$$
3
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

If the function $$f(x) = \left\{ {\matrix{ {{{1 - \cos x} \over {{x^2}}},} & {\mathrm{for}\,x \ne 0} \cr {k,} & {\mathrm{for}\,x = 0} \cr } } \right.$$ is continuous at x = 0, then the value of k is

A
0
B
1
C
$$-$$1
D
1/2
4
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

If $$1,\omega ,{\omega ^2}$$ are the cube roots of unity, then $$(1 + \omega )(1 + {\omega ^2})(1 + {\omega ^4})(1 + {\omega ^8})$$ is equal to

A
0
B
1
C
$$\omega$$
D
$$\omega^2$$
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