RequiredEquations
2D/3D

• RequiredEquations is an option for FindSwitchTime that specifies which equations, of a constraint that restrains more than one degree of freedom, are to be retained in seeking the switch time. RequiredEquations should be a two element list; the first element applies to the first set of equations of the TimeSwitch pair, the second element applies to the second set.
• Allowable values for each element are the following: an integer, a list of integers (1 through the number of degrees of freedom in the constraint), All, or Sum.
• The total number of equations specified must be equal to one plus the number of degrees of freedom constrained by the TimeSwitch.

• If All is given, all the constraints in the associated side of the TimeSwitch constraint are included.
• Sum takes the sum of all equations in the associated side of the TimeSwitch constraint and uses the sum for a single constraint.
• Using the Sum setting can lead to a singularity.
• The normal method of specifying RequiredEquations is to specify All for one side and specify a single integer equation number for the other.
• The default setting is RequiredEquations->{All, Sum}.
• See also: TangentConstraint.