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

If $a=\mathop {\lim }\limits_{n \to \infty } \cos ^{2 n} x,(x=n \pi)$ and $b=\mathop {\lim }\limits_{n \to \infty } \cos ^{2 n} x,(x \neq n \pi)$, then numerical value of the area of the triangle whose vertices are (a, b), (-2, 1) and (2, 1) is

A

2

B

4

C

1

D

$\frac{1}{2}$

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

The position vectors of two adjacent sides $\overrightarrow{O A}$ and $\overrightarrow{O B}$ of a rectangle $O A C B$ are $\vec{a}$ and $\vec{b}$ respectively, where $O$ is the origin. If $16|\vec{a} \times \vec{b}|=3(|\vec{a}|+|\vec{b}|)^2$ and $\theta$ be the acute angle between the diagonals $O C$ and $A B$, then the value of $\tan \left(\frac{\theta}{2}\right)$ is

A

$\frac{1}{3}$

B

$\frac{1}{\sqrt{3}}$

C

$\sqrt{3}$

D

1

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

The point of intersection of $\vec{r} \times \vec{a}=\vec{b} \times \vec{a}$ and $\vec{r} \times \vec{b}=\vec{a} \times \vec{b}$, where $\vec{a}=\hat{i}+\hat{j}$ and $\vec{b}=2 \hat{i}-\hat{k}$ is

A

$3 \hat{i}+2 \hat{j}+\hat{k}$

B

$\hat{i}-\hat{j}-\hat{k}$

C

$4 \hat{i}+2 \hat{j}-\hat{k}$

D

$3 \hat{i}+\hat{j}-\hat{k}$

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

Let $a_1, a_2, a_3 \ldots$ are in G.P. such that $n>m, a_n>a_m$ and $a_1+a_n=66, a_2 \cdot a_{n-1}=128$. If $\sum_{r=1}^n a_r=126$, then $n$ is

A

11

B

8

C

6

D

64