var x=-33204.0924438; //圓心x
var y=-9512.41208658; //圓心y
var r=1000;//半徑
var angle=30;//角度
var tmpX = x + r * Math.Cos(angle * 3.14 / 180);
var tmpY = y + r * Math.Sin(angle * 3.14 / 180);
變換角度0-360
From:https://www.cnblogs.com/xuejianxiyang/p/9354338.html