Geometry

Question Analysis:  
This question involves isosceles triangle properties and angle relationships.  
The main focus is on finding unknown angles and identifying key properties.  

Key Concept Explanation:  
- Isosceles triangles have two equal angles opposite the equal sides.  
- The sum of a triangle’s interior angles is always .  
- The base of an isosceles triangle is the side opposite the unequal angle.  

Step-by-Step Solution:  
1. Since is isosceles with , its base angles are equal.  
  - Given , it follows that .  
2. Using the triangle sum property: