正方体内切球R=a/2;外接球R=a√3/2;棱接球R=a√2/2;
正四面体内切球R=a√6/12;外接球R=a√6/4;棱接球R=a√2/4;
四棱锥内切球R=a(√6-√2)/4;外接球R=a√2/2;棱接球R=a/2;