参考 http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/polygonsrev5.shtml http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/polygonsrev5.shtml http://www.mathsisfun.com/algebra/trig-finding-angle-right-triangle.html http://www.mathsisfun.com/algebra/trig-finding-angle-right-...