ã ã ã
ä¸è¬å°æå¦ä¸è§å¾ï¼é¿æ¹å½¢ä¸ªæ°=[(é¿è¾¹æ®µæ°+1)Ãé¿è¾¹æ®µæ° ÷2][(宽边段æ°+1)Ã宽边段æ°Ã·2]
解ï¼(5+4+3+2+1)Ã(3+2+1)
=(6Ã5÷2)Ã(4Ã3÷2)
=15Ã6
=90 ã
çï¼ä¸å¾ä¸å ±æ90个é¿æ¹å½¢ã ã ã
ã ã ã ã ã