Your position in this diagram is at the top of the circle representing Earth. The angle between your location on the Earth's surface and the equator is, by definition, equal to your latitude (L). A line from the center of the Earth, perpendicular to the equator, northward, emerges from the Earth at the north geographic pole. This line is the top half of the rotational axis of the Earth. The extension of this line an infinite distance locates the north celestial pole (NCP). The angle between your location on the Earth's surface and the north geographic pole is 90 - L (This is called your colatitude). From the diagram, note that the angle between the rotational axis and the line parallel to your horizon, drawn through the center of the Earth is also L (90 - (90 - L)). Therefore, the angle between your horizon and the extension of the Earth's rotational axis to the NCP is also L (see diagram). Since the NCP is an infinite distance away, the angle from a point on your horizon due north of you to the direction of the NCP is also L.