public Vector2D tangent(double t) {
// format between min and max admissible values
t = min(max(0, t), abs(angleExtent));
// compute tangent vector depending on position
if (angleExtent < 0) {
// need to invert vector for indirect arcs
return ellipse.tangent(startAngle - t).times(-1);
} else {
return ellipse.tangent(startAngle + t);
}
}
