A) \[{{c}^{2}}={{a}^{2}}+{{b}^{2}}-ab\]
B) \[{{b}^{2}}={{a}^{2}}+{{c}^{2}}-ac\]
C) \[{{c}^{2}}={{a}^{2}}+{{b}^{2}}\]
D) None of these
Correct Answer: B
Solution :
[b] \[A+C=2B\] and \[A+B+C=180{}^\circ \] so, \[B=60{}^\circ \] \[\therefore \,\,\,\cos \,60{}^\circ =\frac{{{a}^{2}}+{{c}^{2}}-{{b}^{2}}}{2ac}\Rightarrow \,\,{{b}^{2}}={{a}^{2}}+{{c}^{2}}-ac\]
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