Creating a curve tangent to the previous segment by specifying parameters (Tangent Curve)
The Tangent Curve command on the menu that appears when you rightclick the map with a construction tool can be used to add a circular arc curve to an existing segment—for example, to add a curved segment to extend a centerline along a curved road.
When you create a tangent curve with the Tangent Curve command, you must specify two parameters for the curve from the following options: arc length, chord, radius, or delta angle. You must also specify whether you want to create the curve to the right or left of the line, according to the direction in which the line is drawn. The curve is created from the last vertex of the existing segment based on the parameters you define.

These steps can be used to create vertices in either lines or polygons:
To create a vertex in a line
Click a line feature template in the Create Features window and click the Line tool .
To create a vertex in a polygon
Click a polygon feature template in the Create Features window and click the Polygon tool .
 Create a segment using any construction method.
 Rightclick anywhere on the map and click Tangent Curve.
 Click the dropdown arrows and click two parameters by which you want to define the curve.
 Type the appropriate values for the parameters (distance in map units for arc length, chord, and radius; degrees for delta angle).
 Click the Left option to create the tangent curve to the left of the segment. Click the Right option to create the curve to the right.

Press ENTER.
A segment that is a circular arc curve is created from the last vertex of the segment according to the parameters you specified.
If you choose chord length and radius to construct the curve, there are two possible solutions—the major and minor portions of the circle.
The Minor check box appears at the bottom of the Tangent Curve dialog box. Check it to construct the minor portion of the circle.