Circles

Question 1

what is the generic equation of a circle centred at the origin

Answer 1

x^2 + y^2 = r^2

Question 2

equation for circle at any centre

Answer 2

(x - a)^2 + (y - b)^2 = r ^2
centre: (a, b)

Question 3

discriminant of tangent to a circle (one intersection)

Answer 3

b^2 - 4ac = 0

Question 4

discriminant when it does not intersect the circle

Answer 4

b^2 - 4ac < 0

Question 5

discriminant when the line has two points of intersection with the circle

Answer 5

b^2 - 4ac > 0