JEE MAIN - Mathematics (2019 - 8th April Morning Slot)

1
If $$\alpha = {\cos ^{ - 1}}\left( {{3 \over 5}} \right)$$, $$\beta = {\tan ^{ - 1}}\left( {{1 \over 3}} \right)$$ where $$0 < \alpha ,\beta < {\pi \over 2}$$ , then $$\alpha $$ - $$\beta $$ is equal to :
Answer
(B)
$${\sin ^{ - 1}}\left( {{9 \over {5\sqrt {10} }}} \right)$$
2
The area (in sq. units) of the region
A = { (x, y) $$ \in $$ R × R|  0 $$ \le $$ x $$ \le $$ 3, 0 $$ \le $$ y $$ \le $$ 4, y $$ \le $$ x2 + 3x} is :
Answer
(A)
$${{59} \over 6}$$
3
The sum of the solutions of the equation
$$\left| {\sqrt x - 2} \right| + \sqrt x \left( {\sqrt x - 4} \right) + 2 = 0$$
(x > 0) is equal to:
Answer
(D)
10
4
Let A and B be two non-null events such that A $$ \subset $$ B . Then, which of the following statements is always correct?
Answer
(D)
P(A|B) $$ \ge $$ P(A)
5
The sum of all natural numbers 'n' such that 100 < n < 200 and H.C.F. (91, n) > 1 is :
Answer
(B)
3121
6
Let $$A = \left( {\matrix{ {\cos \alpha } & { - \sin \alpha } \cr {\sin \alpha } & {\cos \alpha } \cr } } \right)$$, ($$\alpha $$ $$ \in $$ R)
such that $${A^{32}} = \left( {\matrix{ 0 & { - 1} \cr 1 & 0 \cr } } \right)$$ then a value of $$\alpha $$ is
Answer
(D)
$${\pi \over {64}}$$
7
If $$f(x) = {\log _e}\left( {{{1 - x} \over {1 + x}}} \right)$$, $$\left| x \right| < 1$$ then $$f\left( {{{2x} \over {1 + {x^2}}}} \right)$$ is equal to
Answer
(B)
2f(x)
8
Let O(0, 0) and A(0, 1) be two fixed points. Then the locus of a point P such that the perimeter of $$\Delta $$AOP is 4, is :
Answer
(A)
9x2 + 8y2 – 8y = 16
9
If S1 and S2 are respectively the sets of local minimum and local maximum points of the function,

ƒ(x) = 9x4 + 12x3 – 36x2 + 25, x $$ \in $$ R, then :
Answer
(D)
S1 = {–2, 1}; S2 = {0}
10
If $$f(x) = {{2 - x\cos x} \over {2 + x\cos x}}$$ and g(x) = logex, (x > 0) then the value of integral

$$\int\limits_{ - {\pi \over 4}}^{{\pi \over 4}} {g\left( {f\left( x \right)} \right)dx{\rm{ }}} $$ is
Answer
(C)
loge1
11
The mean and variance of seven observations are 8 and 16, respectively. If 5 of the observations are 2, 4, 10, 12, 14, then the product of the remaining two observations is :
Answer
(B)
48
12
$$\mathop {\lim }\limits_{x \to 0} {{{{\sin }^2}x} \over {\sqrt 2 - \sqrt {1 + \cos x} }}$$ equals:
Answer
(D)
$$4 \sqrt 2$$
13
The length of the perpendicular from the point (2, –1, 4) on the straight line,

$${{x + 3} \over {10}}$$= $${{y - 2} \over {-7}}$$ = $${{z} \over {1}}$$ is :
Answer
(D)
greater than 3 but less than 4
14
A point on the straight line, 3x + 5y = 15 which is equidistant from the coordinate axes will lie only in :
Answer
(A)
1st and 2nd qudratants
15
If $$\alpha $$ and $$\beta $$ be the roots of the equation x2 – 2x + 2 = 0, then the least value of n for which $${\left( {{\alpha \over \beta }} \right)^n} = 1$$ is :
Answer
(C)
4
16
Let y = y(x) be the solution of the differential equation,

$${({x^2} + 1)^2}{{dy} \over {dx}} + 2x({x^2} + 1)y = 1$$

such that y(0) = 0. If $$\sqrt ay(1)$$ = $$\pi \over 32$$ , then the value of 'a' is :
Answer
(B)
$${1 \over 16}$$
17
The greatest value of c $$ \in $$ R for which the system of linear equations
x – cy – cz = 0
cx – y + cz = 0
cx + cy – z = 0
has a non-trivial solution, is :
Answer
(C)
1/2
18
If cos($$\alpha $$ + $$\beta $$) = 3/5 ,sin ( $$\alpha $$ - $$\beta $$) = 5/13 and 0 < $$\alpha , \beta$$ < $$\pi \over 4$$, then tan(2$$\alpha $$) is equal to :
Answer
(D)
63/16
19
$$\int {{{\sin {{5x} \over 2}} \over {\sin {x \over 2}}}dx} $$ is equal to
(where c is a constant of integration)
Answer
(B)
x + 2sinx + sin2x + c
20
All possible numbers are formed using the digits 1, 1, 2, 2, 2, 2, 3, 4, 4 taken all at a time. The number of such numbers in which the odd digits occupy even places is :
Answer
(D)
180
21
If $$2y = {\left( {{{\cot }^{ - 1}}\left( {{{\sqrt 3 \cos x + \sin x} \over {\cos x - \sqrt 3 \sin x}}} \right)} \right)^2}$$,

x $$ \in $$ $$\left( {0,{\pi \over 2}} \right)$$ then $$dy \over dx$$ is equal to:
Answer
(D)
$$x - {\pi \over 6}$$
22
The sum of the squares of the lengths of the chords intercepted on the circle, x2 + y2 = 16, by the lines, x + y = n, n $$ \in $$ N, where N is the set of all natural numbers, is :
Answer
(A)
210
23
Let ƒ : [0, 2] $$ \to $$ R be a twice differentiable function such that ƒ''(x) > 0, for all x $$ \in $$ (0, 2). If $$\phi $$(x) = ƒ(x) + ƒ(2 – x), then $$\phi $$ is :
Answer
(B)
decreasing on (0, 1) and increasing on (1, 2)