To Apply a Tangent Constraint

Select the Constrain Elements tool.
In the tool settings window, set Method to Smart Constrain Elements by selecting the first icon.
Select the first construction.
Select the second construction.
The tangent constraint is displayed. An attempt is made to solve and remove one degree of freedom. The acceptance point determines which solution is selected if there are two solutions or approximately where the solution will be if there is a range of possibilities.

Note: To override or force a tangent constraint, set Method to Constrain Two Constructions to be Tangent by selecting the second icon in the tool settings window.