A) \[(BC)(CA)\]
B) \[-\left( BC \right)\,\,\left( AC \right)\]
C) \[(AB)(BC)\]
D) Zero
Correct Answer: B
Solution :
[b] By cosine law, \[\cos \,60{}^\circ =\frac{A{{C}^{2}}+B{{C}^{2}}-A{{B}^{2}}}{2.AC.BC}=\frac{1}{2}\] \[\Rightarrow \] \[A{{C}^{2}}+B{{C}^{2}}-A{{B}^{2}}=AC\cdot BC\] \[\therefore \]By comparing, we get \[X=-\,(AC)(BC)\] |
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