1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $${Z_r} = \sin {{2\pi r} \over {11}} - i\cos {{2\pi r} \over {11}}$$, then $$\sum\limits_{r = 0}^{10} {{Z_r}} $$ is equal to
A
$$-$$ 1
B
0
C
i
D
$$-$$ i
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If z1 and z2 be two non-zero complex numbers such that $${{{z_1}} \over {{z_2}}} + {{{z_2}} \over {{z_1}}} = 1$$, then the origin and the points represented by z1 and z2
A
lie on a straight line
B
form a right angled triangle
C
form an equilateral triangle
D
form an isosceles triangle
3
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $${a_r} = {(\cos 2r\pi + i\sin 2r\pi )^{1/9}}$$,

then the value of $$\left| {\matrix{ {{a_1}} & {{a_2}} & {{a_3}} \cr {{a_4}} & {{a_5}} & {{a_6}} \cr {{a_7}} & {{a_8}} & {{a_9}} \cr } } \right|$$ is equal to
A
1
B
$$-$$ 1
C
0
D
2
4
WB JEE 2018
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let z1 and z2 be complex numbers such that z1 $$ \ne $$ z2 and |z1| = |z2|. If Re(z1) > 0 and Im(z2) < 0, then $${{{z_1} + {z_2}} \over {{z_1} - {z_2}}}$$ is
A
one
B
real and positive
C
real and negative
D
purely imaginary
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EXAM MAP
Medical
NEET
Graduate Aptitude Test in Engineering
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CBSE
Class 12