TAN \left( \frac{B-C}{2} \right)=\frac{b-c}{b+c}\COT \frac{A}{2}\] Þ \[\tan \left( \frac{90{}^\circ }{2} \right)=\frac{\sqrt{3}-1}{\sqrt{3}+1}\cot \frac{A}{2}\] Þ \[\tan \left( \frac{A}{2} \right)=\frac{\sqrt{3}-1}{\sqrt{3}+1}=\frac{3+1-2\sqrt{3}}{2}=2-\sqrt{3}\] Þ \[\frac{A}{2}={{15}^{o}}\Rightarrow A={{30}^{o}}\].