/// <summary>
/// Returns one possible tangent vector of this <see cref="GreatCircle"/> in the given point, the other is antipodal to it.
/// </summary>
/// <param name="point">The point on the <see cref="GreatCircle"/> that the tangent is wanted for.</param>
/// <returns>One possible tangent vector.</returns>
public CartesianVector GetTangentAt(CartesianVector point)
{
return(DefinitionVector.CrossProduct(point).AsUnitVector);
}
/// <summary>
/// Creates a new instance of the <see cref="GreatCircle"/> struct given two points defining it.
/// </summary>
/// <param name="start">The start coordinate of the segment.</param>
/// <param name="end">The end coordinate of the segment.</param>
public GreatCircle(CartesianVector start, CartesianVector end)
: this(start.CrossProduct(end))
{
}