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Mathematics
Mathematics
Problem
The vectors
2
i
^
−
m
j
^
+
3
m
k
^
2\hat{i} - m\hat{j} + 3m\hat{k}
2
i
^
−
m
j
^
+
3
m
k
^
and
(
1
+
m
)
i
^
−
2
m
j
^
+
k
^
(1+m)\hat{i} - 2m\hat{j} + \hat{k}
(
1
+
m
)
i
^
−
2
m
j
^
+
k
^
include an acute angle for (A) all real
m
m
m
(B)
m
<
−
2
m < -2
m
<
−
2
or
m
>
−
1
2
m > -\frac{1}{2}
m
>
−
2
1
(C)
m
=
−
1
2
m = -\frac{1}{2}
m
=
−
2
1
(D)
m
∈
[
−
2
,
−
1
2
]
m \in [-2, -\frac{1}{2}]
m
∈
[
−
2
,
−
2
1
]
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