[Choose the one correct answer and explain your reasoning.]
The circle in the diagram has centre \(C\). Three angles \(\alpha, \beta, \gamma\) are also indicated.
The angles \(\alpha,\beta, \gamma\) are related by the equation:
\(\cos \alpha = \sin (\beta + \gamma)\),
\(\sin \beta = \sin \alpha \sin \gamma\),
\(\sin \beta (1 − \cos \alpha) = \sin \gamma\),
\(\sin (\alpha + \beta) = \cos \gamma \sin \alpha\).