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Mathematics
Mathematics
Problem
For what value of
k
k
k
does the angle between the vectors
⟨
k
,
1
,
−
1
⟩
\langle k,\,1,\,-1\rangle
⟨
k
,
1
,
−
1
⟩
and
⟨
1
,
k
,
−
1
⟩
\langle 1,\,k,\,-1\rangle
⟨
1
,
k
,
−
1
⟩
become
120
∘
120^\circ
12
0
∘
? a)
0
0
0
b)
−
2
-2
−
2
c)
−
4
-4
−
4
d)
2
2
2
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