The Arctic Circle lies at 67 degrees north. How does that number follow from the 23 degree tilt?

1. At the June solstice the Sun lights everywhere within 23 degrees of the North Pole for a full day. 2. The pole itself sits at 90 degrees north. 3. Take 23 degrees away from 90 degrees and you reach 67 degrees north. 4. That is the southernmost latitude with 24 hours of sunshine, the Arctic Circle. _Source: OpenStax Astronomy (CC BY 4.0), Ch 4 "Earth, Moon, and Sky" and Ch 5 "Radiation and Spectra", section 4.2 The Seasons_