1
WB JEE 2026
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If $\sum\limits_{r=1}^{\infty} \tan ^{-1}\left(\frac{1}{2 r^2}\right)=a$, then $\tan a$ is equal to

A

1

B

0

C

$\sqrt{3}$

D

$\frac{\pi}{4}$

2
WB JEE 2026
MCQ (Single Correct Answer)
+1
-0.25
Change Language

Consider a function $f(x)$ which has exactly two roots at $x=a$. If $\mathop {\lim }\limits_{x \to a}\left(\frac{\lambda f^{\prime}(x)}{f(x)}-\frac{1}{x-a}\right)=m(\neq 0)$, then the value of $\lambda$ ix

A

2

B

1

C

$\frac{1}{2}$

D

$\frac{1}{4}$

3
WB JEE 2026
MCQ (Single Correct Answer)
+1
-0.25
Change Language

A vector given by $\vec{P}=f(t) \hat{i}+g(t)+\hat{k}$ moves in such a way that it is always parallel to the vector $\vec{Q}=-f^{\prime \prime}(t) \hat{i}+f^{\prime}(t) \hat{j}+\hat{k}$.

A

a linear function of time

B

a quadratic function of time

C

a cubic function of time

D

constant

4
WB JEE 2026
MCQ (Single Correct Answer)
+1
-0.25
Change Language

The expression $\sum_{k=1}^{32}(3 K+2)\left\{\sum_{r=1}^{10}\left(\sin \frac{2 r \pi}{11}-i \cos \frac{2 r \pi}{11}\right)\right\}^k$ represents

A

$48(1+\mathrm{i})$

B

$-48(1-\mathrm{i})$

C

$-\frac{48}{11}(1-\mathrm{i})$

D

$48(1-\mathrm{i})$