ÌâÄ¿ÄÚÈÝ
£¨2011•¿ª·âһģ£©ÒÑÖªÍÖÔ²C£º
+
=1£¨a£¾b£¾0£©µÄÉÏÏîµãΪB1£¬ÓÒ¡¢ÓÒ½¹µãΪF1¡¢F2£¬¡÷B1F1F2ÊÇÃæ»ýΪ
µÄµÈ±ßÈý½ÇÐΣ®
£¨I£©ÇóÍÖÔ²CµÄ·½³Ì£»
£¨II£©ÒÑÖªP£¨x0£¬y0£©ÊÇÒÔÏ߶ÎF1F2Ϊֱ¾¶µÄÔ²ÉÏÒ»µã£¬ÇÒx0£¾0£¬y0£¾0£¬Çó¹ýPµãÓë¸ÃÔ²ÏàÇеÄÖ±ÏßlµÄ·½³Ì£»
£¨III£©ÈôÖ±ÏßlÓëÍÖÔ²½»ÓÚA¡¢BÁ½µã£¬Éè¡÷AF1F2£¬¡÷BF1F2µÄÖØÐÄ·Ö±ðΪG¡¢H£¬ÇëÎÊÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚÂð£¿ÈôÔÚÇë˵Ã÷ÀíÓÉ£®
x2 |
a2 |
y2 |
b2 |
3 |
£¨I£©ÇóÍÖÔ²CµÄ·½³Ì£»
£¨II£©ÒÑÖªP£¨x0£¬y0£©ÊÇÒÔÏ߶ÎF1F2Ϊֱ¾¶µÄÔ²ÉÏÒ»µã£¬ÇÒx0£¾0£¬y0£¾0£¬Çó¹ýPµãÓë¸ÃÔ²ÏàÇеÄÖ±ÏßlµÄ·½³Ì£»
£¨III£©ÈôÖ±ÏßlÓëÍÖÔ²½»ÓÚA¡¢BÁ½µã£¬Éè¡÷AF1F2£¬¡÷BF1F2µÄÖØÐÄ·Ö±ðΪG¡¢H£¬ÇëÎÊÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚÂð£¿ÈôÔÚÇë˵Ã÷ÀíÓÉ£®
·ÖÎö£º£¨I£©ÀûÓÃÈý½ÇÐεÄÃæ»ý¹«Ê½ºÍµÈ±ßÈý½ÇÐεÄÐÔÖʿɵÃ
b•2c=
£¬a=2c£¬ÓÖa2=b2+c2£®¼´¿É½â³ö£®
£¨¢ò£©ÓÉF1F2ÊÇÔ²µÄÒ»ÌõÖ±¾¶£¬¿ÉµÃÔ²µÄ·½³ÌΪx2+y2=1£®ÓÖP£¨x0£¬y0£©ÊǸÃÔ²ÔÚµÚÒ»ÏóÏÞ²¿·ÖÉϵÄÇÐÏßµÄÇе㣬¿ÉµÃkl•
=-1£¬½âµÃkl=-
£®¿ÉµÃÇÐÏß·½³ÌΪy-y0=-
(x-x0)£¬ÓÖ
+
=1£¬¼´¿ÉµÃ³ö£»£®
£¨III£©ÉèA£¨x1£¬y1£©£¬B£¨x2£¬y2£©£¬¾ÝÖØÐĶ¨Àí¿ÉµÃG(
£¬
)£¬H(
£¬
)£®ÈôÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚ?
•
£¼0?x1x2+y1y2£¼0£¬ÁªÁ¢
£¬¿ÉµÃy1+y2£¬y1y2£¬ÓÖx1x2=
•
£¬¼´¿ÉÖ¤Ã÷x1x2+y1y2£¼0£®
1 |
2 |
3 |
£¨¢ò£©ÓÉF1F2ÊÇÔ²µÄÒ»ÌõÖ±¾¶£¬¿ÉµÃÔ²µÄ·½³ÌΪx2+y2=1£®ÓÖP£¨x0£¬y0£©ÊǸÃÔ²ÔÚµÚÒ»ÏóÏÞ²¿·ÖÉϵÄÇÐÏßµÄÇе㣬¿ÉµÃkl•
y0 |
x0 |
x0 |
y0 |
x0 |
y0 |
x | 2 0 |
y | 2 0 |
£¨III£©ÉèA£¨x1£¬y1£©£¬B£¨x2£¬y2£©£¬¾ÝÖØÐĶ¨Àí¿ÉµÃG(
x1 |
3 |
y1 |
3 |
x2 |
3 |
y2 |
3 |
OH |
OG |
|
1-y0y1 |
x0 |
1-y0y2 |
x0 |
½â´ð£º½â£º£¨I£©¡ß
b•2c=
£¬a=2c£¬a2=b2+c2£®
½âµÃc2=1£¬b2=3£¬a2=4£¬
¡àÍÖÔ²CµÄ·½³ÌΪ£º
+
=1
£¨¢ò£©¡ßF1F2ÊÇÔ²µÄÒ»ÌõÖ±¾¶£¬¡àÔ²µÄ·½³ÌΪx2+y2=1£¬
ÓÖP£¨x0£¬y0£©ÊǸÃÔ²ÔÚµÚÒ»ÏóÏÞ²¿·ÖÉϵÄÇÐÏßµÄÇе㣬
¡àkl•
=-1£¬½âµÃkl=-
£®
¡àÇÐÏß·½³ÌΪy-y0=-
(x-x0)£¬ÓÖ
+
=1£¬
»¯Îªl£ºx0x+y0y-1=0£®
¡àÇÐÏß·½³ÌΪl£ºx0x+y0y-1=0£®
£¨III£©ÉèA£¨x1£¬y1£©£¬B£¨x2£¬y2£©£¬ÔòG(
£¬
)£¬H(
£¬
)£®
ÈôÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚ£¬Ôò
•
£¼0£¬¼´
+
£¼0£¬¼´x1x2+y1y2£¼0£¬
ÏÂÃæ¸ø³öÖ¤Ã÷£ºÁªÁ¢
£¬
ÏûÈ¥xÕûÀíΪ(4
+3
)y2-6y0y+3-12
=0£¬
¡ày1+y2=
£¬y1y2=
£¬
¡àx1x2=
•
=
=
£¬
¡àx1x2+y1y2=
=-
£¼0£®
¡àÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚ£®
1 |
2 |
3 |
½âµÃc2=1£¬b2=3£¬a2=4£¬
¡àÍÖÔ²CµÄ·½³ÌΪ£º
x2 |
4 |
y2 |
3 |
£¨¢ò£©¡ßF1F2ÊÇÔ²µÄÒ»ÌõÖ±¾¶£¬¡àÔ²µÄ·½³ÌΪx2+y2=1£¬
ÓÖP£¨x0£¬y0£©ÊǸÃÔ²ÔÚµÚÒ»ÏóÏÞ²¿·ÖÉϵÄÇÐÏßµÄÇе㣬
¡àkl•
y0 |
x0 |
x0 |
y0 |
¡àÇÐÏß·½³ÌΪy-y0=-
x0 |
y0 |
x | 2 0 |
y | 2 0 |
»¯Îªl£ºx0x+y0y-1=0£®
¡àÇÐÏß·½³ÌΪl£ºx0x+y0y-1=0£®
£¨III£©ÉèA£¨x1£¬y1£©£¬B£¨x2£¬y2£©£¬ÔòG(
x1 |
3 |
y1 |
3 |
x2 |
3 |
y2 |
3 |
ÈôÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚ£¬Ôò
OH |
OG |
x1x2 |
9 |
y1y2 |
9 |
ÏÂÃæ¸ø³öÖ¤Ã÷£ºÁªÁ¢
|
ÏûÈ¥xÕûÀíΪ(4
x | 2 0 |
y | 2 0 |
x | 2 0 |
¡ày1+y2=
6y0 | ||||
4
|
3-12
| ||||
4
|
¡àx1x2=
1-y0y1 |
x0 |
1-y0y2 |
x0 |
1-y0(y1+y2)+
| ||
|
4-12
| ||||
4
|
¡àx1x2+y1y2=
7-12(
| ||||
4
|
5 | ||
|
¡àÔµãOÔÚÒÔÏ߶ÎGHΪֱ¾¶µÄÔ²ÄÚ£®
µãÆÀ£º±¾Ì⿼²éÁËÍÖÔ²µÄ±ê×¼·½³Ì¼°ÆäÐÔÖÊ¡¢Ö±ÏßÓëÍÖÔ²ÏཻÎÊÌâת»¯Îª·½³ÌÁªÁ¢µÃµ½¸ùÓëϵÊýµÄ¹Øϵ¡¢ÏòÁ¿ÊýÁ¿»ýÔËËã¡¢Ö±ÏßÓëÔ²ÏàÇС¢µãÓëÔ²µÄλÖùØϵÅж¨µÈ»ù±¾ÖªÊ¶Óë»ù±¾¼¼ÄÜ£¬¿¼²éÁË·ÖÎöÎÊÌâºÍ½â¾öÎÊÌâµÄÄÜÁ¦¡¢ÍÆÀíÄÜÁ¦Óë¼ÆËãÄÜÁ¦£®£®
Á·Ï°²áϵÁдð°¸
Ïà¹ØÌâÄ¿