$\left| \overline{\varepsilon } \right|=\left| -N\frac{\Delta \Phi }{\Delta t} \right|\Rightarrow \left| \overline{\varepsilon } \right|=\frac{\Delta (BA\,\operatorname{Cos}\theta )}{\Delta t}=A\times \frac{\Delta B}{\Delta t}\times \operatorname{Cos}\theta \Rightarrow \left| \overline{\varepsilon } \right|=0/5\times 2\times \operatorname{Cos}\,{{30}^{\circ }}=0/5\times \frac{\sqrt{3}}{2}\times 2=\frac{\sqrt{3}}{2}V$