| 释义 |
〔center〕A point equidistant from all points on the circumference of a circle or on the surface of a sphere.圆心，球心：与一圆周上或一球面上所有点等距的一点〔steradian〕A unit of measure equal to the solid angle subtended at the center of a sphere by an area on the surface of the sphere that is equal to the radius squared:立体弧度：由球心所张成的立体角，它在球面上所截取平面的面积等于以球半径为边长的正方形面积： |