From the figure, we can see that the angles ∠CRB and ∠ERA are vertical angles. This means that they are congruent:
[tex]\begin{gathered} ∠CRB\cong∠ERA \\ \\ \Rightarrow m∠ERA=50\degree \end{gathered}[/tex]
Finally, since this is a central angle, we conclude that:
[tex]EA=50\degree[/tex]
