Subjects geometry

Star Angles

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1. **Problem Statement:** Given a star with 10 points, the sum of the outer angles labeled \(\angle 1 + \angle 2 + \cdots + \angle 9 = 266^\circ\). Find the sum of the inner angles \(\angle a + \angle b + \cdots + \angle i\). 2. **Key Concept:** For any polygon, the sum of the exterior angles is always \(360^\circ\). Here, the outer angles \(\angle 1\) through \(\angle 9\) are part of the exterior angles of the star polygon. 3. **Calculation:** Since the star has 10 points, there are 10 exterior angles in total. The sum of all exterior angles is \(360^\circ\). 4. Given \(\angle 1 + \angle 2 + \cdots + \angle 9 = 266^\circ\), the tenth exterior angle is: $$\angle 10 = 360^\circ - 266^\circ = 94^\circ$$ 5. The inner angles \(\angle a\) through \(\angle i\) correspond to the angles inside the star between points, which are related to the exterior angles by: $$\text{Inner angle} = 180^\circ - \text{Exterior angle}$$ 6. Since there are 9 inner angles \(a\) through \(i\), and 9 corresponding exterior angles \(1\) through \(9\), their sums relate as: $$\sum_{k=a}^i \angle k = 9 \times 180^\circ - \sum_{k=1}^9 \angle k = 1620^\circ - 266^\circ = 1354^\circ$$ **Final answer:** \(\angle a + \angle b + \angle c + \angle d + \angle e + \angle f + \angle g + \angle h + \angle i = 1354^\circ\).