−20246510xy3x+2y−11=0(1,4) x2+y2−6x+8y−11=0rO(3,−4)R circle to encoderO(4,−2)r=5 x2+y2+4x−6y−12=0rO(−2,3)R m=4/3tangent m=−3/4O(1,2)P(4,6) tangentO(1,2)P(4,6)(0,9) O(1,2)P(4,6)normal m=4/3tangent x2+y2=25y=x+1OPQ x2+y2−6x+2y−6=0rO(3,−1)R Mathematics 2 · Coordinate geometry in the (x, y)-plane