1
WB JEE 2024
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If $$A=\left(\begin{array}{cc}\cos \theta & -\sin \theta \\ \sin \theta & \cos \theta\end{array}\right)$$ and $$\theta=\frac{2 \pi}{7}$$, then $$A^{100}=A \times A \times \ldots .(100$$ times) is equal to

A
$$ \left(\begin{array}{cc} \cos 2 \theta & -\sin 2 \theta \\ \sin 2 \theta & \cos 2 \theta \end{array}\right) $$
B
$$ \left(\begin{array}{cc} \cos \theta & -\sin \theta \\ \sin \theta & \cos \theta \end{array}\right) $$
C
$$ \left(\begin{array}{ll} 1 & 0 \\ 0 & 1 \end{array}\right) $$
D
$$ \left(\begin{array}{cc} 0 & -1 \\ 1 & 0 \end{array}\right) $$
2
WB JEE 2024
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If $$\left(1+x+x^2+x^3\right)^5=\sum_\limits{k=0}^{15} a_k x^k$$ then $$\sum_\limits{k=0}^7(-1)^{\mathbf{k}} \cdot a_{2 k}$$ is equal to

A
25
B
45
C
0
D
44
3
WB JEE 2024
MCQ (Single Correct Answer)
+1
-0.25
Change Language

The coefficient of $$a^{10} b^7 c^3$$ in the expansion of $$(b c+c a+a b)^{10}$$ is

A
140
B
150
C
120
D
160
4
WB JEE 2024
MCQ (Single Correct Answer)
+1
-0.25
Change Language

$$ \text { If }\left|\begin{array}{lll} x^k & x^{k+2} & x^{k+3} \\ y^k & y^{k+2} & y^{k+3} \\ z^k & z^{k+2} & z^{k+3} \end{array}\right|=(x-y)(y-z)(z-x)\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}\right) \text {, then } $$

A
k = $$-$$3
B
k = 3
C
k = 1
D
k = $$-$$1
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