Circumscribed circle

A triangle $ABC$ is circumscribed by a circle with center $O$ . The arcs $AB , BC$ and $AC$ subtend the angles $\alpha , \beta$ and $\gamma$ respectively at $O$ .

If the area of the circle is $50\pi$ square units and that of the triangle is $15$ square units , find the value of $\sin\alpha + \sin\beta + \sin\gamma$ .

Give your answer correct to 3 significant figures.