import math


def mag_inc(x, y, z):
    """
    Given *x* (north intensity), *y* (east intensity), and *z*
    (vertical intensity) all in [nT], return the magnetic inclincation
    angle [deg].
    """
    h = math.sqrt(x**2 + y**2)
    return math.degrees(math.atan2(z, h))