ÌâÄ¿ÄÚÈÝ

¾«Ó¢¼Ò½ÌÍøÈçͼ£¬¾ØÐÎֽƬABCDÖУ¬AB=4£¬BC=4
3
£¬½«¾ØÐÎÑضԽÇÏßAC¼ô¿ª£¬½â´ðÒÔÏÂÎÊÌ⣺
£¨1£©ÔÚ¡÷ACDÈƵãC˳ʱÕëÐýת60¡ã£¬¡÷A1CD1ÊÇÐýתºóµÄÐÂλÖã¨Í¼A£©£¬Çó´ËAA1µÄ¾àÀ룻
£¨2£©½«¡÷ACDÑضԽÇÏßACÏòÏ·­ÕÛ£¨µãA¡¢µãCλÖò»¶¯£¬¡÷ACDºÍ¡÷ABCÂäÔÚͬһƽÃæÄÚ£©£¬¡÷ACD2ÊÇ·­ÕÛºóµÄÐÂλÖã¨Í¼B£©£¬Çó´ËʱBD2µÄ¾àÀ룻
£¨3£©½«¡÷ACDÑØCBÏò×óƽÒÆ£¬ÉèƽÒƵľàÀëΪx£¨0¡Üx¡Ü4
3
£©£¬¡÷A2C1D3ÊÇƽÒƺóµÄÐÂλÖã¨Í¼C£©£¬Èô¡÷ABCÓë¡÷A2C1D3Öصþ²¿·ÖµÄÃæ»ýΪy£¬Çóy¹ØÓÚxµÄº¯Êý¹Øϵʽ£®
¾«Ó¢¼Ò½ÌÍø¾«Ó¢¼Ò½ÌÍø¾«Ó¢¼Ò½ÌÍø
·ÖÎö£º£¨1£©Óɹ´¹É¶¨Àí¿ÉµÃAC³¤¶È£¬ÓÉÓÚAC=A1C£¬ÒòΪ¡ÏACA1=60¡ã£¬ËùÒÔ¡÷ACA1ΪµÈ±ßÈý½ÇÐΣ¬ÄÇôAA1=AC
£¨2£©Ò×µÃBD2ÊǵÈÑüÌÝÐεÄÉϵף¬ÄÇô¿É¹ýÌÝÐÎÉϵ×Á½¸ö¶Ëµã×÷ϵ׵Ĵ¹Ïߣ¬µÃµ½Á½¸öÈ«µÈµÄÖ±½ÇÈý½ÇÐΣ¬°ÑËùÇóÏ߶ÎתÒƵ½Ïµ×Çó½â£®
£¨3£©Ò×µÃÒõÓ°²¿·ÖΪƽÐÐËıßÐΣ¬ÄÇô¿É¸ù¾ÝÏàÓ¦µÄÈý½Çº¯ÊýÇóµÃÒõÓ°²¿·ÖµÄµ×Óë¸ß£®
½â´ð£º½â£º£¨1£©ÔÚRt¡÷ABCÖУ¬Óɹ´¹É¶¨ÀíµÃ£¬AC=
AB2+BC2
=
42+(4
3
)
2
=8
£¬
ÔÚ¡÷ACA1ÖУ¬¡ßAC=A1C£¬¡ÏACA1=60¡ã£¬
¡à¡÷ACA1ΪµÈ±ßÈý½ÇÐΣ®
¡àAA1=AC=8£®£¨4·Ö£©

£¨2£©Èçͼ2Ëùʾ£¬¹ýB£¬D2·Ö±ð×÷BE¡ÍACÓÚE£¬D2F¡ÍACÓÚF£¬ÔòBE¡ÎD2F£¬
ÔÚRt¡÷ABCÖУ¬¡ßAB=4£¬BC=4
3
£¬tan¡ÏBAC=
BC
AB
=
4
3
4
=
3
£¬
¡à¡ÏBAC=60¡ã£®
ÔÚRt¡÷ABEÖУ¬AB=4£¬¡ÏBAE=60¡ã£¬¡ÏABE=30¡ã£¬
¡àAE=
1
2
AB=2£¬BE=2
3
£®
ͬÀí£¬CF=2£¬D2F=2
3
£¬
¡àEF=AC-AE-CF=8-2-2=4£¬
¡ßBE
¡Î
.
.
D2F
£¬
¡àËıßÐÎBEFD2ÊÇƽÐÐËıßÐΣ¬
¡àBD2=EF=4£®£¨8·Ö£©

£¨3£©Èçͼ3Ëùʾ£¬AA2=x£¬AG=
3
3
x£¬AD3=4
3
-x
£¬
¡ßƽÒƵĸÅÄî¼°¾ØÐεÄÐÔÖʵÃAG¡ÎC1H£¬GC1¡ÎAH£¬
¡àËıßÐÎAGC1HÊÇƽÐÐËıßÐΣ¬
¡ày=SƽÐÐËıßÐÎAGC1H=AG•AD3=
3
3
x•(4
3
-x)=-
3
3
x2+4x
£¨0¡Üx¡Ü4
3
£©£®£¨12·Ö£©
¾«Ó¢¼Ò½ÌÍø¾«Ó¢¼Ò½ÌÍø¾«Ó¢¼Ò½ÌÍø
µãÆÀ£ºÐýתǰºó£¬·­ÕÛÇ°ºóµÃµ½µÄ¶ÔÓ¦Ï߶κͽǶ¼ÏàµÈ£¬×÷µÈÑüÌÝÐεÄÁ½¸ß¹¹ÔìÖ±½ÇÈý½ÇÐÎÊdz£Óõĸ¨ÖúÏß·½·¨£®
Á·Ï°²áϵÁдð°¸
Ïà¹ØÌâÄ¿

Î¥·¨ºÍ²»Á¼ÐÅÏ¢¾Ù±¨µç»°£º027-86699610 ¾Ù±¨ÓÊÏ䣺58377363@163.com

¾«Ó¢¼Ò½ÌÍø