Problem:
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Tangent to a Circle

Find the tangent lines between a point $p$ and a circle $c$.

Input

The input is given in the following format.

$px \; py$

$cx \; cy \; r$

$px$ and $py$ represents the coordinate of the point $p$. $cx$, $cy$ and $r$ represents the center coordinate and radius of the circle $c$ respectively. All input values are given in integers.

Output

Print coordinates of the tangent points on the circle $c$ based on the following rules.

Print the coordinate with smaller $x$ first. In case of a tie, print the coordinate with smaller $y$ first.

The output values should be in a decimal fraction with an error less than 0.00001.

Constraints

$-1,000 \leq px, py, cx, cy \leq 1,000$

$1 \leq r \leq 1,000$

Distance between $p$ and the center of $c$ is greater than the radius of $c$.

Sample Input 1

0 0
2 2 2

Sample Output 1

0.0000000000 2.0000000000
2.0000000000 0.0000000000

Sample Input 2

-3 0
2 2 2

Sample Output 2

0.6206896552 3.4482758621
2.0000000000 0.0000000000

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using static Exg;
static class Program{
	const int mod=(int)1e9+7;
	const double eps=1e-11;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Da;
		var a=sc.Da;
		var e=Gp13(new Pair(a[0],a[1]),a[2],new Pair(s[0],s[1]));
		Array.Sort(e,(u,v)=>u.x.CompareTo(v.x));
		Console.WriteLine(e[0]);
		Console.WriteLine(e[1]);
	}
}

public struct Pair{
	public double x,y;
	public Pair(double x,double y){this.x=x;this.y=y;}
	public Pair(double[] da){x=da[0];y=da[1];}
	public Pair(Pair p){x=p.x;y=p.y;}
	public override string ToString()=>x.ToString()+" "+y.ToString();
	public static Pair operator+(Pair a,Pair b){a.x+=b.x;a.y+=b.y;return a;}
	public static Pair operator-(Pair a,Pair b){a.x-=b.x;a.y-=b.y;return a;}
	public static Pair operator*(Pair a,double n){a.x*=n;a.y*=n;return a;}
	public static Pair operator/(Pair a,double n){a.x/=n;a.y/=n;return a;}
}
static class Exg{
	static public Pair[] Gp13(Pair p1,double r,Pair a){
		a-=p1;
		double g=a.x*a.x+a.y*a.y,k=Sqrt(g-r*r);
		return new Pair[]{new Pair(r*(a.x*r+a.y*k)/g,r*(a.y*r-a.x*k)/g)+p1,new Pair(r*(a.x*r-a.y*k)/g,r*(a.y*r+a.x*k)/g)+p1};
	}
}
public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),int.Parse);}
	public int[] Ia3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),long.Parse);}
	public long[] La3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),double.Parse);}
	public double[] Da3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}