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Question : 31 of 160
Marks:
+1,
-0
Solution:
From the given equation,
cosα=,cosβ= ,cosλ= Then,
cosα+cosβ+cosγ =(a.b+bc+c.a) Use the relation,
|a+b+c|2=[|a|2+|b|2+|c|2 +2(a.b+b.c+ca)] We can write
[λ2+λ2+λ2+2(a.b+b.c+c.a)]≥0 2(a.b+b.c+c.a)≥−3λ2 a.b+b.c+c.a> Then
cosα+cosβ+cosγ≥( )=− Therefore, the minimum value of the required equation is
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