Choose Inspect tab→Analyze group→Curvature Comb Settings.
On the Curvature Comb Settings dialog box, click the Show Curvature Curve Settings option.
Click on a 3D curve.
Tip:
You can also click the Clear All Combs option on the Curvature Comb Settings dialog box to clear the display of all curvature combs. To display the Curvature Comb Settings dialog box choose Inspect tab→Analyze group→Curvature Comb Settings.
Curvature Comb Settings command