Correct Answer: length of the arc of the great circle passing through them
3. If ? and ? be the latitude of a place and declination of a star respectively, the upper culmination of the star will be north of zenith if its zenith distance, is
4. If ?, H, A and ? be the altitude, hour angle, azimuth and declination of a circumpolar star at its elongation, in latitude ?, the following relation holds good