The measure of an arc can be found by dividing that arc's length (s) by the circle's radius (r). (s/r) = (arc's length / circle's radius) The resulting answer is written in radians, and can be converted to degrees by multiplying that number of radians by 180, then dividing by...
although the limit of resolution of the unaided eye (i.e., the ability to separate points visually) is no better than about 3×10-4radians or about one minute of arc, the capability of the human eye is, however, much greater