å¤ææ¹æ³ï¼
1ãçæºçµæºåå«æ¯ä¸¤ä¸ªç»ç»ï¼ç¨ä¸ç¨åå«æµé线åçµé»ã
2ãæ¾å°ä¸¤ä¸ªçº¿ååï¼æ两个线åçæ¥ï¼å¨å¼åºä¸æ ¹ï¼æ¤æ¶å°±åªæä¸æ ¹çº¿äºã
3ãéè¿æµéçµé»æ大çä¸¤æ ¹çº¿æ¥çµå®¹ï¼å¦å¾ï¼ã
4ãçµé»æå°çä¸¤æ ¹çº¿æ¥çµæºLãNã