Derive a relation between one parsec and one light year.

Explanation

To derive a relation between one parsec and one light year, we will follow these steps:

### Step 1: Define the units
- **Parsec (pc)**: A unit of length used in astronomy to measure large distances. It is defined as the distance at which one astronomical unit subtends an angle of one arcsecond.
- **Light Year (ly)**: The distance that light travels in a vacuum in one year.

### Step 2: Convert parsec to meters
- The value of one parsec is given as:
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