getTangentAt method
u - A position on the curve according to the arc length. Must
be in the range 0, 1 .
optionalTarget — (optional) If specified, the result will be
copied into this Vector, otherwise a new Vector will be created.
Returns tangent at a point which is equidistant to the ends of the curve from the point given in getTangent.
Implementation
Vector getTangentAt(double u, [Vector? optionalTarget]) {
final t = getUtoTmapping(u);
return getTangent(t, optionalTarget);
}