radian equals to

If the measures of three angles of quadrilateral are and 90° respectively, then let us determine and write the sexagesimal and circular values of fourth angle.

The end point of the minute hand of a clock rotates in 1 hour

The circular value of each internal angle of a regular hexagon is

The measurement of Θ in the relations to S=rΘ is determined by

A. sexagesimal system

B. circular system

C. Those two methods

D. None of these