Changes

<math>\,\!s \approx \frac {180 \times 3600}{p \times \pi}</math>

<math>\,\!s \approx \frac {180 \times 3600}{p \times \pi}</math>

where p is measured in seconds of arc.

where pi is measured in seconds of arc.

The cotangent of one second (1/3600 of a degree) of arc is approximately 206,264.81. No parallax angle for any star will be larger than one second. Therefore astronomers initially defined a unit of stellar distance, the ''parsec'' (symbol pc), from this relationship. One parsec is the distance corresponding to a parallax angle of one second of arc. Hence:

The cotangent of one second (1/3600 of a degree) of arc is approximately 206,264.81. No parallax angle for any star will be larger than one second. Therefore astronomers initially defined a unit of stellar distance, the ''parsec'' (symbol pc), from this relationship. One parsec is the distance corresponding to a parallax angle of one second of arc. Hence: