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 1: Understand the given data
We have the following information:
- Diameter of the sun, \( d \)
- Angle subtended by the sun at the pole of the mirror, \( \theta \) (in radians)
- Focal length of the concave mirror, \( f \)

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