Question

The angle of 1" (second of arc) in a radian is equal to:

(1) 4.85 × 10^–4

(2) 4.85 × 10^–6

(3) 1.75 × 10^–2

(4) 1.75 × 10^–4

Answer 1

A minute of arc is π/10800 of a radian. A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol ″, is 1/60 of an arcminute, 1/3600 of a degree, 1/1296000 of a turn, and π/648000 (about 1/206369)

so answer is,

(2) 4.85 × 10^–6