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How many astronomical units (A.U.) make 1 parsec?
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Solution
1 A.U. long arc subtends the angle of 1 s or 1 arc sec at distance of 1 parsec.
Thus, angle 1 sec = `(1 A.U.)/1` parsec
Thus, 1 parsec = `(1 A.U.)/1` arc sec
Thus, 1 parsec = `(630(3600))/11`
= 206182.8
= 2 × 10^{5} A.U.
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