Complete will not extract a tangent constraint for a pair of elements unless the elements themselves (not their extensions) are tangent. Solve, however, recognizes linear and circular extensions when adjusting for tangency.

Solve attempts to maintain as much of the current configuration as possible when adjusting to satisfy tangency constraints. When adjusting a circular and a linear element to be tangent, Solve attempts to keep the circle on the same side of the line as it was originally. When adjusting two circles to be tangent, effort is taken to ensure that if one circle is inside the other, it remains inside, and that circles which are outside of each other stay that way.