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Mathematics
Mathematics
Problem
Consider a
△
A
B
C
\triangle ABC
△
A
B
C
where
A
(
1
,
3
,
2
)
A(1, 3, 2)
A
(
1
,
3
,
2
)
,
B
(
−
2
,
8
,
0
)
B(-2, 8, 0)
B
(
−
2
,
8
,
0
)
and
C
(
3
,
6
,
7
)
C(3, 6, 7)
C
(
3
,
6
,
7
)
. If the angle bisector of
∠
B
A
C
\angle BAC
∠
B
A
C
meets the line
B
C
BC
B
C
at
D
D
D
, then the length of the projection of the vector
A
D
⃗
\vec{AD}
A
D
on the vector
A
C
⃗
\vec{AC}
A
C
is:
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