1
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
A vector $$\overrightarrow a = \alpha \widehat i + 2\widehat j + \beta \widehat k\left( {\alpha ,\beta \in R} \right)$$ lies in the plane of the vectors, $$\overrightarrow b = \widehat i + \widehat j$$ and $$\overrightarrow c = \widehat i - \widehat j + 4\widehat k$$. If $$\overrightarrow a$$ bisects the angle between $$\overrightarrow b$$ and $$\overrightarrow c$$, then:
A
$$\overrightarrow a .\widehat i + 3 = 0$$
B
$$\overrightarrow a .\widehat k - 4 = 0$$
C
$$\overrightarrow a .\widehat i + 1 = 0$$
D
$$\overrightarrow a .\widehat k + 2 = 0$$
2
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
Let $$\alpha$$ $$\in$$ R and the three vectors $$\overrightarrow a = \alpha \widehat i + \widehat j + 3\widehat k$$, $$\overrightarrow b = 2\widehat i + \widehat j - \alpha \widehat k$$ and $$\overrightarrow c = \alpha \widehat i - 2\widehat j + 3\widehat k$$. Then the set S = {$$\alpha$$ : $$\overrightarrow a$$ , $$\overrightarrow b$$ and $$\overrightarrow c$$ are coplanar}
A
contains exactly two numbers only one of which is positive
B
is singleton
C
contains exactly two positive numbers
D
is empty
3
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
Let $$\overrightarrow a = 3\widehat i + 2\widehat j + 2\widehat k$$ and $$\overrightarrow b = \widehat i + 2\widehat j - 2\widehat k$$ be two vectors. If a vector perpendicular to both the vectors $$\overrightarrow a + \overrightarrow b$$ and $$\overrightarrow a - \overrightarrow b$$ has the magnitude 12 then one such vector is :
A
$$4\left( {2\widehat i - 2\widehat j - \widehat k} \right)$$
B
$$4\left( { - 2\widehat i - 2\widehat j + \widehat k} \right)$$
C
$$4\left( {2\widehat i + 2\widehat j + \widehat k} \right)$$
D
$$4\left( {2\widehat i + 2\widehat j - \widehat k} \right)$$
4
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
If the volume of parallelopiped formed by the vectors $$\widehat i + \lambda \widehat j + \widehat k$$, $$\widehat j + \lambda \widehat k$$ and $$\lambda \widehat i + \widehat k$$ is minimum, then $$\lambda$$ is equal to :
A
$$- {1 \over {\sqrt 3 }}$$
B
$${\sqrt 3 }$$
C
$$-{\sqrt 3 }$$
D
$${1 \over {\sqrt 3 }}$$
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