A) \[{{a}^{2}}-{{b}^{2}}\]
B) \[{{b}^{2}}-{{c}^{2}}\]
C) \[{{c}^{2}}-{{a}^{2}}\]
D) \[{{a}^{2}}+{{b}^{2}}+{{c}^{2}}\]
Correct Answer: B
Solution :
\[a(b\cos C-c\cos B)=ab\cos C-ac\cos B\] = \[\frac{{{a}^{2}}+{{b}^{2}}-{{c}^{2}}}{2}-\frac{{{a}^{2}}+{{c}^{2}}-{{b}^{2}}}{2}={{b}^{2}}-{{c}^{2}}\].
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