1.å¹³å§æ¨ä¸¾ï¼ä¸»è¦ç»è¸å¤§èçå度åè¸æ²ã
å¨ä½ï¼ä¸¤ææåéä»°å§å³ä¸ï¼åéç½®äºè©é¨ï¼æå¿æä¸ï¼ä¸æ¨åéè³è伸ç´ï¼ç¨åï¼ç¶åç¼æ ¢è¿åãæ示ï¼ä¸æ¨åä¸éå弧线ï¼ä½¿è¸å¤§èå¾å°å åæ¶ç¼©åå½»åºä¼¸å±ã
.å¹³å§é£é¸ï¼ä¸»è¦ç»è¸é¨ä¸é´æ²ã
å¨ä½ï¼ä»°å§å³ä¸ï¼ä¸¤ææåéï¼æå¿ç¸å¯¹ï¼ä¸¤èèªç¶ä¼¸ç´äºè¸é¨ä¸æ¹ï¼ä¸¤èå¾®å±èå两侧弧形ä¸æ¾åéè³æä½ç¹ï¼è¸èå å伸å±ï¼è¸èç¨åæ¶ç¼©å°ä¸¤è弧形ä¸ä¸¾è¿åã