ban oi bai toan khao sat t lam tn k biet dung k nua
1)goi M(x0,y0) la diem can tim, viet pttt wa M co hsg la k: y= kx +yM
viet dk tiep xuc cua tt va dthi (C), tim dk de he pt co 2 ngiem theo Y0
hinh nhu la y0>1/2 ay(b kt lai nha) dai khai la dk theo y0
sau do tim dk de 2tt doi xung wa oy, t lam ntn, la minh tim dk de 2 tiep diem dx nhau wa oy, way ve bai toan tiem tren (c) 2 diem dx wa 1dt cho truoc. cach lam cu the t wen roi huhu
theo to doan mo thi lam tn.
2)goi delta la pt dt vuong goc voi oy, tim dk de delta cat (c) theo 2tiep diem...A,B
goi I la trung diem A,B suy ra Xi= XA+XB/2..YI tuong tu...giai theo Ym (I thuoc oy)...kai doan 2 nay sai sao i, b lam tiep nha