using System;
using L=Science.Physics.GeneralPhysics;

namespace Serway.Chapter23
{
	/// <summary>
	/// Example09: The Electric Field of a Uniformly Charged Disk
	/// A disk of radius R has a uniform surface charge density 
	/// \sigma. Calculate the electric field at a point P that
	/// lies along the central perpendicular axis of the disk
	/// and a distance x from the center of the disk.
	/// E_x = 2\pi k_e \sigma ( 1 - x /(x^2 + R^2)^{1/2})	
	/// </summary>
	public class Example09
	{
		public Example09()
		{
		}
		private string result;
		public string Result
		{
			get{return result;}
		}
		double ke = L.Constant.CoulombConstant;
		double sigma  = 10.0; // sigma = Q / (Math.PI R^2)
		double R = 2.0;
		double x = 3.0;
		double y = 0.00000000001;
		double z = 0.00000000001;
		L.Position r = new L.Position();
		L.Position rp = new L.Position();
		public void Compute()
		{
			rp.X = x;
			rp.Y = y;
			rp.Z = z;

            L.Vector proj = new L.Vector();

			L.Calculus.Function<double[],double> Ex
				= new L.Calculus.Function<double[],double>(funcx);
			double[] r = {0.0,0.0};
			double[] rt = {R, 2.0*Math.PI};
            double[] res = L.Calculus.IntegrationMultiD(Ex, r, rt);
            proj.X = res[0];
            proj.StandardDeviationOfX = res[1];

            L.Calculus.Function<double[], double> Ey
                = new L.Calculus.Function<double[], double>(funcy);
            res = L.Calculus.IntegrationMultiD(Ey, r, rt);
            proj.Y = res[0];
            proj.StandardDeviationOfY = res[1];


            L.Calculus.Function<double[], double> Ez
                = new L.Calculus.Function<double[], double>(funcz);
            res = L.Calculus.IntegrationMultiD(Ez, r, rt);
            proj.Z = res[0];
            proj.StandardDeviationOfZ = res[1];
			

			result+=proj.ToString()+"\r\n ";  
			result+=Convert.ToString(2.0*Math.PI*ke*sigma
				*(1.0 - x /Math.Sqrt(x*x + R*R)));  
		}
		private double funcx(double[] rtheta)
		{
			r.X = 0.0;
			r.Y = rtheta[0]*Math.Cos(rtheta[1]);
			r.Z = rtheta[0]*Math.Sin(rtheta[1]);
			
			L.ElectricCharge q = new L.ElectricCharge();
			q.C = sigma*rtheta[0];
			L.ElectricField E = new L.ElectricField(q,r,rp);
			return E.X;
		}
		private double funcy(double[] rtheta)
		{
			r.X = 0.0;
			r.Y = rtheta[0]*Math.Cos(rtheta[1]);
			r.Z = rtheta[0]*Math.Sin(rtheta[1]);
			
			L.ElectricCharge q = new L.ElectricCharge();
			q.C = sigma*rtheta[0];
			L.ElectricField E = new L.ElectricField(q,r,rp);
			return E.Y;
		}
		private double funcz(double[] rtheta)
		{
			r.X = 0.0;
			r.Y = rtheta[0]*Math.Cos(rtheta[1]);
			r.Z = rtheta[0]*Math.Sin(rtheta[1]);
			
			L.ElectricCharge q = new L.ElectricCharge();
			q.C = sigma*rtheta[0];
			L.ElectricField E = new L.ElectricField(q,r,rp);
			return E.Z;
		}
	}
}
/*
94841965772.6548 +/- 257867.405761845 i    -414791.381599429 +/- 369279.737985012 j     +475637.831721448 +/- 368684.532583328 k    
94841413676.1735
*/