def sphericalPolar_2_cartesian(positionVectorSphericalPolar):
    """Convert spherical-polar coordinates (in radians), into Cartesian coordinates.

The origin of the Cartesian frame of reference is located at the centre of the sphere, the positive half of x-axis goes through 0 deg E, 0 deg N, the positive half of y-axis goes through 90 deg E, 0 deg N and the positive half of the z-axis goes through the North Pole equivalent."""
    import numpy as np
    [radius, theta, phi] = positionVectorSphericalPolar
    x = radius * np.sin(theta) * np.cos(phi)
    y = radius * np.sin(theta) * np.sin(phi)
    z = radius * np.cos(theta)
    return [x, y, z]
