Question
How many astronomical units (A.U.) make 1 parsec?

Answer

According to the definition, 1 parsec is equal to the distance at which 1AU long arc subtends an angle of 1s.
$\text{But}\ \ 1''=\frac{1}{3600}\times\frac{\pi}{180}\text{rad}$
$\therefore1\text{parsec}=\frac{3600\times180}{\pi}\text{AU}$
$=206265\text{AU}\approx2\times10^5\text{AU}$

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