Garis singgung lingkaran x2 +y2 -4x +8y +10 = 10 tegak lurus garis x +3y - 15 = 0 adalah

ruas kanan dianggap 0 bukan 10, jika mang 10, cara perhitungannya sama² saja
x^2 +y^2 - 4x +8y +10 = 0
A = -4, B = 8 dan C = 10
 Pusat = (-A/2, -B/2) = (2, -4)
r = √(2² + (-4)²) - C) = √(4 + 16 - 10) = √10
3y = -x + 15 → m = -1/3
tgklurus → m1 = -1/m = -1/(-1/3) = 3
y - b = m1(x - a) ± r√(1 + m1²)
y + 4 = 3(x - 2) ± √10√(1 + 3²)
PGS 1 dan 2
y = 3x - 10 ± 10