Let D,E,F be the middle points of the sides BC,CA,AB respectively of a triangle ABC. Then →AD+→BE+→CF equals
A
→0
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B
2→AB
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C
3→AB
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D
None of these
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Solution
The correct option is A→0 Let the position vector of A,B,C be →a,→b,→c respectively. THen, the position vectors of D,E,F are →b+→c2,→c+→a2,→a+→b2 respectively. Therefore. →AD+→BE+→CF =(→b+→c2−→a)+(→c+→a2−→b)+(→a+→b2−→c) =12[→b+→c−2→a+→c+→a−2→b+→a+→b−2→c]=→0