Find all polar coordinates of point p where p = (5,-pi/6)

P (x, y) = (5,  - π/6 )
x = 5
y = -π/6
polar coordinates :  (r , Ф) where
x = r cos Ф      and  y  =  r sin Ф
r = √(x² + y²)              Ф = inverse tan (y/x)
r = √(25 + π²/36)  =  √(900+π²)  / 6    =  5.03
Ф = inverse tan  -π/(6*5)  =    - 5.98 deg  =  - 0.1 radians
polar coordinates =  (5.03, - 0.1 )

Ithink it's b sorry if i'm wrong