Setting Tangency Continuity between curves - Modify Common point and adjust both

The Modify common point and adjust both option of the Curve Continuity command applies tangency continuity by modifying the shared endpoint.
 

3	Select the two curves. If a curve is specialized and not a NURBS, you are asked to confirm whether you want to convert it into a NURBS (unless you have deselected the Ask before converting check box). Tolerance for converting into NURBS You can control the way the curve is converted by setting a suitable Tolerance value. The lower the tolerance value, the more accurate the resulting NURBS will be and, hence, the more control points it will have.
4	In the 1st Weight and 2nd Weight mini-dialog boxes, type the values of weight for the two curves. The Weights Each curve can be associated with a numeric value - its weight - which indicates how much the curve is to be modified relative to the other. The higher the weight, the less the curve changes. If the weight of a curve is zero, the other curve is not modified at all. The weight of a curve is a value between 0 and 1.
5	To check the position of control points, select Show Control Points under More Options. The Tangent angle box shows the tangent angle value in the common point.
6	Click or to confirm your selections and modify the curves. Click to discard your changes.