设地心为O,A、B所在纬线圆心为P,则角OAP或OBP的度数即为x.
可得圆心角AOB=п/3,则弦长AB=R.可得角APB=90度,则AP=根号下2/2*R,cos角OAP=AP/OA=根号下2/2,即角OAP=45度,x=45.