1
WB JEE 2025
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If ' $\theta$ ' is the angle between two vectors $\vec{a}$ and $\vec{b}$ such that $|\vec{a}|=7,|\vec{b}|=1$ and $|\vec{a} \times \vec{b}|^2=k^2-(\vec{a} \cdot \vec{b})^2$, then the values of $k$ and $\theta$ are

A
$k=1, \theta=45^{\circ}$
B
$k=7, \theta=60^{\circ}$
C
$k=49, \theta=90^{\circ}$
D
$k=7$ and $\theta$ is arbitrary
2
WB JEE 2025
MCQ (Single Correct Answer)
+1
-0.25
Change Language

Consider three points $P(\cos \alpha, \sin \beta), Q(\sin \alpha, \cos \beta)$ and $R(0,0)$, where $0<\alpha, \beta<\frac{\pi}{4}$. Then

A
$P$ lies on the line segment $R Q$.
B
$Q$ lies on the line segment $P R$.
C
$R$ lies on the line segment $P Q$.
D
$P, Q, R$ are non-collinear.
3
WB JEE 2025
MCQ (Single Correct Answer)
+1
-0.25
Change Language

An $n \times n$ matrix is formed using 0, 1 and $-$1 as its elements. The number of such matrices which are skew symmetric is

A
$\frac{n(n-1)}{2}$
B
$(n-1)^2$
C
$2^{n(n-1) / 2}$
D
$3^{n(n-1) / 2}$
4
WB JEE 2025
MCQ (Single Correct Answer)
+1
-0.25
Change Language

Suppose $\alpha, \beta, \gamma$ are the roots of the equation $x^3+q x+r=0($ with $r \neq 0)$ and they are in A.P. Then the rank of the matrix $\left(\begin{array}{lll}\alpha & \beta & \gamma \\ \beta & \gamma & \alpha \\ \gamma & \alpha & \beta\end{array}\right)$ is

A
3
B
2
C
0
D
1
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