You can add continuity relations for tangency and equal curvature to certain sketch entities as soon as you finish sketching them on existing geometry.
You add the continuity relations when you select a shared endpoint between two entities using the Constraint pop-up toolbar. The toolbar appears when the following sketch entities terminate on:
- A line and an arc
- A style spline and a spline
- Model edges
- Conic, parabola and partial ellipse entities
To apply continuity relations:
- Open a new sketch. Use the 3 Point Arc
tool to sketch an arc.
- Click Spline
(Sketch toolbar) or . Sketch a spline at some distance away from the arc.
- Snap the spline to the arc's endpoint and double click to terminate the spline.
The Constraint pop-up toolbar displays.
- Click Tangent
or Equal Curvature 
from the pop-up toolbar.