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Mathematics
Mathematics
Problem
If
∣
c
⃗
∣
2
=
60
|\vec{c}|^2 = 60
∣
c
∣
2
=
60
and
c
⃗
×
(
i
^
+
2
j
^
+
5
k
^
)
=
0
⃗
\vec{c} \times (\hat{i} + 2\hat{j} + 5\hat{k}) = \vec{0}
c
×
(
i
^
+
2
j
^
+
5
k
^
)
=
0
, then a value of
c
⃗
⋅
(
−
7
i
^
+
2
j
^
+
3
k
^
)
\vec{c} \cdot (-7\hat{i} + 2\hat{j} + 3\hat{k})
c
⋅
(
−
7
i
^
+
2
j
^
+
3
k
^
)
is : (1)
4
2
4\sqrt{2}
4
2
(2) 24 (3)
12
2
12\sqrt{2}
12
2
(4) 12
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