in any triangle ABC, the value of \sum{} a(b2+c2) cosA is
1) 3 abc 2)3(a2+b2+c2)
3)a2+b2+c2 4)abc
answer: 1)3 abc
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3 Answers
39simple jee way of doing this is
if u put a=b=c
u find all 4 options in answer come out different
so substitute that and u r there at your answer
62for a 50-50 lifeline you could even say that options 2 and 3 are wrong dimensionally :)