Thus, polygon draws a 50-sides polygon that approximates a circle with radius r.
polygon画一个50边的多边形，来近似做一个半径为r的圆。
If you start from that North Pole as centre, then the circle with radius equal to a half meridian is the equator, and the area included is the northern hemisphere.
如果你以北极点为中心开始画圆，那么半径和半个子午线相等的圆周就是赤道，它包含的区域就是北半球。
What you need from a search service is a PHP page that takes a latitude and longitude pair, along with a radius, and returns any articles that have a location with that circle.
对于搜索服务，您需要的是一个php页面，该页面使用纬度和经度对以及半径，并且返回与该圆具有一定位置关系的任何文章。
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