1
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
A spherical iron ball of 10 cm radius is coated with a layer of ice of uniform thickness the melts at a rate of 50 cm3/min. When the thickness of ice is 5 cm, then the rate (in cm/min.) at which of the thickness of ice decreases, is :
A
$${1 \over {18\pi }}$$
B
$${1 \over {36\pi }}$$
C
$${1 \over {54\pi }}$$
D
$${5 \over {6\pi }}$$
2
JEE Main 2020 (Online) 8th January Evening Slot
+4
-1
Out of Syllabus
The length of the perpendicular from the origin, on the normal to the curve,
x2 + 2xy – 3y2 = 0 at the point (2,2) is
A
$$\sqrt 2$$
B
$$4\sqrt 2$$
C
2
D
$$2\sqrt 2$$
3
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
Out of Syllabus
If c is a point at which Rolle's theorem holds for the function,
f(x) = $${\log _e}\left( {{{{x^2} + \alpha } \over {7x}}} \right)$$ in the interval [3, 4], where a $$\in$$ R, then ƒ''(c) is equal to
A
$${1 \over {12}}$$
B
$${{\sqrt 3 } \over 7}$$
C
$$-{1 \over {12}}$$
D
$$-{1 \over {24}}$$
4
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
Let ƒ(x) = xcos–1(–sin|x|), $$x \in \left[ { - {\pi \over 2},{\pi \over 2}} \right]$$, then which of the following is true?
A
ƒ' is decreasing in $$\left( { - {\pi \over 2},0} \right)$$ and increasing in $$\left( {0,{\pi \over 2}} \right)$$
B
ƒ '(0) = $${ - {\pi \over 2}}$$
C
ƒ is not differentiable at x = 0
D
ƒ' is increasing in $$\left( { - {\pi \over 2},0} \right)$$ and decreasing in $$\left( {0,{\pi \over 2}} \right)$$
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