|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
1/2 circle or half circle is equal to 360°/2 = 180°. Plural name is helf circles.
A second of arc, arcsecond (arcsec), arc second, or second arc is a unit of angular measurement equal to 1/3600 of one degree.