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Mathematics
Mathematics
Problem
If
D
D
D
,
E
E
E
and
F
F
F
are the middle points of the sides
B
C
BC
B
C
,
C
A
CA
C
A
and
A
B
AB
A
B
of the
Δ
A
B
C
\Delta ABC
Δ
A
B
C
, then
A
D
+
B
E
+
C
F
\mathbf{AD} + \mathbf{BE} + \mathbf{CF}
AD
+
BE
+
CF
is a. a zero vector b. a unit vector c. 0 d. None of these
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