خارجی $\widehat{A}=\frac{\overset\frown{EC}-\overset\frown{BD}}{2}$ $\overset{\Delta }{\mathop{AOE}}\,$ زاویه خارجی مثلث  $E\widehat{O}C=\widehat{E}+\widehat{A}=64{}^\circ $ زاویه مرکزی  $E\widehat{O}C=\overset\frown{EC}=64{}^\circ $ $24=\frac{64-\overset\frown{BC}}{2}\Rightarrow 48=64-\overset\frown{BD}$  $\overset\frown{BD}=64-48\Rightarrow \overset\frown{BD}=16{}^\circ $