This does not change the magnitude of the tangent vector, only its direction.
Unless the direction
the spline is running is known, there is a 50% chance that the effect
of the editing may not make the spline take the desired shape. This is
because splines run in only one direction, from one end to the other.
If the spline was running in the direction other than the one assumed,
the editing may have changed the direction of the tangent vector by more
than 90°, and an unexpected loop or curve may have appeared.
To correct this, simply reverse the
magnitude of the tangent
vector edited. In other words, if the magnitude is .76 make it -.76. This
can be done by using the Magnitude command.
This can be avoided by using the Line Tangent command on this menu
to display the vectors that indicate the spline direction.