Geometry

Question Analysis

The main focus is using the property that a tangent to a circle is perpendicular to the radius at the point of tangency. We know  is tangent to  at , so . Then we can use the angle - sum property of a triangle to find .

 

Key Concept Explanation

A tangent line to a circle is perpendicular to the radius at the point of tangency, creating a right - angle. In , we know one angle () and another (), and we use the fact that the sum of the interior angles of a triangle is  to find the third angle.

 

Step - by - Step Solution

1. Recall the angle - sum property of a triangle: In , .

2. Since  is tangent to

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