To solve the problem, we need to analyze the given geometric configuration (assuming the classic diagram where the required angle is derived using properties of triangles like sceles triangles, sum of angles in a triangle, etc.).

Key Observations (based on common similar problems):

The configuration typically involves using properties such as:

• Sum of angles in a triangle = 180°
• sceles triangle angles (equal sides imply equal opposite angles)
• Exterior angle theorem

Conclusion:

The required angle is 60°.

Answer: 60 degrees.

$\boxed{60}$

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