Question

lines should not cross the circle​

Answer 1

If a line crosses half of the circle then it's a radius.

Answer 2

Answer:

If we obtain two coincident roots, then the line is touching the circle at only one point (i.e. two coincident points). ... Positive means intersection at two distinct points, zero implies tangency, and a negative sign would mean the line doesn't intersect or touch the circle. Here's a figure to summarize what I just said.