What is the condition for the line y=mx+cy = mx + cy=mx+c to be a tangent to the circle x2+y2=r2x^2 + y^2 = r^2x2+y2=r2?
c2=r2(1+m2)c^2 = r^2(1+m^2)c2=r2(1+m2)
c2=r2(1−m2)c^2 = r^2(1-m^2)c2=r2(1−m2)
c=rmc = r\sqrt{m}c=rm
c=m2rc = m^2rc=m2r