External tangency
= External tangency
{title2=$|c_1-c_2|=r_1+r_2$}
Two distinct positive-<radius> <circles> have external tangency when their closed <disks> meet at exactly one point. The <Euclidean distance> between their centres equals the sum of their <radii>. The contact point divides the segment of centres internally in the ratio $r_1:r_2$.