1£®“a = l”ÊÇ“º¯Êý ÔÚÇø¼ä ÉÏΪÔöº¯Êý”µÄ £¨ £©
A£®³ä·Ö²»±ØÒªÌõ¼þ B£®±ØÒª²»³ä·ÖÌõ¼þ
C£®³äÒªÌõ¼þ D£®¼È²»³ä·ÖÒ²²»±ØÒªÌõ¼þ
2£®Éè £¬ÇÒ ÎªÕýʵÊý£¬Ôòa = £¨ £©
A£® 2 B£® 1 C£® 0 D£® -1
3£®¼ºÖªÈ«¼¯ £¬¼¯ºÏ £¬ £¬Èô
£¬ÄÇô £¨ £©
A£® a=-1 B£® C£® a = l D£®
4£®ÈýÀâ׶P—ABCµÄÁ½²àÃæPAB¡¢PBC¶¼ÊDZ߳¤Îª2aµÄÕýÈý½ÇÐΣ¬ £¬Ôò¶þÃæ½ÇA—PB—CµÄ´óСΪ £¨ £©
A£®90° B£®30° C£®45° D£®60°