An equilateral triangle of side 9 cm is inscribed in a circle. Find the radius of the circle.

Explanation

To find the radius of the circle in which an equilateral triangle of side 9 cm is inscribed, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Properties of the Equilateral Triangle**:
- An equilateral triangle has all sides equal and all angles equal to 60 degrees. Here, the side length \( a = 9 \) cm.

2. **Draw the Triangle and Perpendiculars**:
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