Modifying the tangent vector magnitude, while keeping its direction unchanged

To modify the magnitude of the tangent vector of a curve in a certain point without modifying its direction, start the Curve Shape Constraint command and proceed as follows.

1	Select the curve by clicking on the location you want to edit. A handle will be displayed on the curve in the location you selected.
	You are now enabled to change the curve shape by moving the location you selected on it or by modifying the tangency conditions in the same location.
2	To move the selected location without modifying the tangency conditions, proceed as follows:

• Right-click on the tangent vector and select Set Tan Magnitude. The handle extension changes as you move the mouse. Click to fix the new length of the vector.
  
  or
  
  
• Click on the handle in a location which is 3/4 of the length between the middle point of the handle and an end point. The handle extension changes as you move the mouse, while holding down the mouse button. Release the mouse button to fix the new length of the vector.