See, whenever we are talking of a ship here, this is my u 1, this is my V, this is my v, this is my beta u 1 equal to V cos beta and v equal to V sin beta, beta is small u 1 V, v equal to beta, sorry no here v equal to sorry v beta. So, this is what we do, because normally the heading angle will be small, you know you do not have a ship going like this 45 degree angle, it will be may be 10 degree or so. Although, I write for the sake of this thing a ship will not travel like this, you know it will travel with small angle only. So, beta is normally 10 degree or so not much unless you make a very large simulation.