Impedance of R-L network

Hi,

If i want to find the total impedance of an R-L series network would i:

a) |Z| = R + (2*PI*f*L)

b) |Z| = sqrt( R^2 + (2*PI*f*L)^2 )

?? I can't decide which one it should be. I think it should be a) as it is only adding in series. But then, it is a complex number so the magnitude is the roots of squares. Help?

-Peter

The correct answer is b).
The tangent of the phase angle is XL/R

Thanks!