上周末作业评讲 yoF1F2x1A1B2A2B11)1(FA和若过)221,3(此时圆心257d21)2(FA和若过)253,1(此时圆心27d11)3(FB 和若过)27578310,91988()27578310,91988(或此时圆心为:解:圆心到直线的距离|12||1|22mmmmmd|2|12mm 222111mmmd21||2mmd||12mm rd2)1,0( 另解:直线过定点在圆上又)1,0( 直线与圆相交
FxOyACBD||||||||BCADCDAB解:pxxAD21||4||BC)0,2()0,2(为圆心又pF4 p4282xyxy0462xx6446|| AB
FxOyABP),(),,(2211yxByxA解:设22212122pxypxy2121212yypxxyy相减0ypkAB 60100xykAB又06xp8||||21pxxBFAF又820 px即xyx8,220抛物线为:OyxAB34112222abac)解:(223ba 2322baab又1322yx双曲线方程为:OyxAB1322yx双曲线方程为:),(00 yxMCD的中点为设131322222121yxyx)(3:21212121yyxxxxyy相减得003yxk 即500kxy又2020315,3115kykkxkkxykk52110200 时,当7 k33522yxkxy联立530||CD方程有解,且782||0CDk时,满足题意,当782530||或 CDF2xy