What are the angular diameters in appropriate units eg 0001

What are the angular diameters (in appropriate units, e.g. 0.001 = 1 mas or 1800 =30 ) of the following, as seen from Earth?

a) The Sun.
b) Betelgeuse, with MV = 5.5, mV = 0.8, and R = 650R.
c) The galaxy M31, with R 30 kpc at a distance of D 0.7 Mpc.

a) andular diameter q = 2 arctan (d / 2D)

d diameter if the star , D is the distance to the star

for sun d = 10^6 km and D = 149.6 * 10 ^6

q = 2 arctan ( 10^6 / 149.6 * 10 ^6 )

~0.765 radians

b) distance to Betelgeuse in parsec is D = 10 ^{[mv - MV )+5 ]/ 5}

D = 10 ^{[0.8-(-5.5)+5 ]/ 5}

D = 181.970 parsecs

and d = 2* 650Ro = 2* 650 * 2.257 * 10^-8 parsecs

for Betelgeuse q = 2 arctan (d / 2D)

= 2 arctan (2* 650 * 2.257 * 10^-8 / 181.970 )

= 1.847*10^-5 radians

c. The galaxy M31

q = 2 arctan (d / 2D)

= 2 arctan (2 * 30 * 10^3 pc / 0.7 * 10 ^6 pc)

= 9.798 radians