The radian is the angle created by two radii  R  and an arc who's length is also equal to the radius R, So one radian is equal to  57.3  degrees compare to  60  degrees of an equilateral triangle. Because the circumference of a circle is  2πR  a complete circle has  2π  radians and half circle has 180 degrees which is  π  radian.

The earth is divided into longitudes extends from the north pole to the south pole and divides it into  360  degrees staring from  0  degree at Greenwich observatory in London and increasing degree eastward. The latitude divides the distance from the equatorial to the north pole by 90 degrees north and from the equatorial to the south pole by  90 degrees  south enables to describe any point on earth by the proper coordinates of longitude and latitude.

Protractor of 180 degrees used to measure drawings angles and directions on maps.