1. 半徑為1997, 2008, 2013的三個圓兩兩外切,並且這三個圓都內切於圓O,則圓O的半徑為______。
2. 是否存在五角星形,使得AB = 1998, BC = 1999, CD = 2001, DE = 2003, EF = 2005, FG = 2007, GH = 2009, HI = 2011, IJ = 2013, JA = 2014?
圖片參考:http://imgcld.yimg.com/8/n/HA06399860/o/20130211185859.jpg