1. The problem statement, all variables and given/known data I've got a radius of 22.69kpc, and a velocity of 180km/s. I wish to find the angular rotation speed in units of arcsec/year. I'm stuck at the moment 3. The attempt at a solution Starting with the basic v=r[tex]\omega[/tex], I transpose to get [tex]\omega[/tex]=v/r. For now, I'm going to convert all length units to parsec, and all time units to years. velocity = 180km/s = (5.83*10^-12)pc/s = (1.84*10^-4)pc/year radius = 22.69kpc = 22690pc [tex]\omega[/tex] = [(1.84*10^-4)pc/year]/[22690pc] = (8.11*10^-9) yr^-1 since the units of parsec cancel This is where I'm stuck, how do I ge the arcsec units in?