1
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let R be the real line. Let the relations S and T or R be defined by

$$S = \{ (x,y):y = x + 1,0 < x < 2\} ,T = \{ (x,y):x - y$$ is an integer}. Then
A
both S and T are equivalence relations on R
B
T is an equivalence on R but S is not
C
neither S nor T is an equivalence relation on R
D
S is an equivalence relation on R but T is not
2
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
The plane lx + my = 0 is rotated about its line of intersection with the plane z = 0 through an angle $$\alpha$$. The equation changes to
A
$$lx + my \pm \tan \alpha \sqrt {{l^2} + {m^2}} = 0$$
B
$$lx + my \pm z\tan \alpha \sqrt {{l^2} + {m^2} + 1} = 0$$
C
$$lx + my \pm z\tan \alpha \sqrt {{l^2} + 1} = 0$$
D
$$lx + my \pm z\tan \alpha \sqrt {{l^2} + {m^2}} = 0$$
3
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
The points of intersection of two ellipses $${x^2} + 2{y^2} - 6x - 12y + 20 = 0$$ and $$2{x^2} + {y^2} - 10x - 6y + 15 = 0$$ lie on a circle. The centre of the circle is
A
(8, 3)
B
(8, 1)
C
$$\left( {{8 \over 3},3} \right)$$
D
(3, 8)
4
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let $$I = \int_{\pi /4}^{\pi /3} {{{\sin x} \over x}dx} $$. Then
A
$${{\sqrt 3 } \over 8} \le I \le {{\sqrt 2 } \over 6}$$
B
$${{\sqrt 3 } \over {2\pi }} \le I \le {{2\sqrt 3 } \over \pi }$$
C
$${{\sqrt 3 } \over 9} \le I \le {{\sqrt 2 } \over {16}}$$
D
$$\pi \le I \le {{4\pi } \over 3}$$
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