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