Garis singgung lingkaran x2 + y2 - 2x +20y - 68 = 0 di titik (6,2) memotong sumbu y di titik ...... A. (0,-4 1/2) B. (0,4 1/2) C. (0,-3 1/2) D. (0,3 1/2) E. 0,-

jawab

x^2 + y^2 - 2x + 20y -68 = 0
(x -1)^2 + (y+10)^2 = 68+1+100 = 169
a= 1
b = -10
r^2= 169

titik singgung (6,2)
(6-1)(x -1) + (2+10)(y+10) = 169
5(x -1) + 12(y+10) = 169
titikpotong dgnsumbu y, x = 0
5(0-1) + 12(y+10)= 169
12(y+10) = 169+5  = 174
(y+10) = 14 1/2
y = 4 1/2

titk pot ( 0, 4 1/2)