The sun (diameter `d`) subtends an angle `theta` radian at the pole of a concave mirror of focal length `f`. What is the diameter of the image of the sun formed by the mirror ?

Explanation

To find the diameter of the image of the sun formed by a concave mirror, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a concave mirror with a focal length \( f \).
- The sun, which has a diameter \( D \), subtends an angle \( \theta \) at the pole of the mirror.

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