A) \[abc\]
B) \[2\,abc\]
C) \[3\,abc\]
D) \[4\,abc\]
E) 0
Correct Answer: C
Solution :
\[({{b}^{2}}+{{c}^{2}})a\cos A+({{c}^{2}}+{{a}^{2}})b\cos B+\] \[({{a}^{2}}+{{b}^{2}})c\cos C\] \[=ab(b\cos A+a\cos B)+\] \[bc(b\cos C+c\cos B)+ca(a\cos C+c\cos A)\] \[=abc++abc+abc=3abc\]You need to login to perform this action.
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