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Problems
If
u
=
i
^
×
(
a
×
i
^
)
+
j
^
×
(
a
×
j
^
)
+
k
^
×
(
a
×
k
^
)
\mathbf{u} = \hat{i} \times (\mathbf{a} \times \hat{i}) + \hat{j} \times (\mathbf{a} \times \hat{j}) + \hat{k} \times (\mathbf{a} \times \hat{k})
u
=
i
^
×
(
a
×
i
^
)
+
j
^
×
(
a
×
j
^
)
+
k
^
×
(
a
×
k
^
)
…
Mathematics
Problem
If
u
=
i
^
×
(
a
×
i
^
)
+
j
^
×
(
a
×
j
^
)
+
k
^
×
(
a
×
k
^
)
\mathbf{u} = \hat{i} \times (\mathbf{a} \times \hat{i}) + \hat{j} \times (\mathbf{a} \times \hat{j}) + \hat{k} \times (\mathbf{a} \times \hat{k})
u
=
i
^
×
(
a
×
i
^
)
+
j
^
×
(
a
×
j
^
)
+
k
^
×
(
a
×
k
^
)
, then a.
u
=
0
\mathbf{u} = 0
u
=
0
b.
u
=
i
^
+
j
^
+
k
^
\mathbf{u} = \hat{i} + \hat{j} + \hat{k}
u
=
i
^
+
j
^
+
k
^
c.
u
=
2
a
\mathbf{u} = 2\mathbf{a}
u
=
2
a
d.
u
=
a
\mathbf{u} = \mathbf{a}
u
=
a
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