From the vertex of an equilateral triangle we draw the ray which intersects the side at . On we consider a point such that . Find the angle .
Solutions — 2
Solution 1
Since , point is the circumcenter of the triangle . The angle is inscribed to the circle and so:
Solution 2
From and , we have , and the triangle is isosceles. We draw the altitude from , let , .

Then is also median and bisector of the angle of the triangle . Let meet at . Then the triangles and are equal because they have:

Therefore we have: and since
Thus quadrilateral is inscribable, and hence:
Finally we get:
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