User:Jonjoseph

$[asy] pair O = (0,0); pair P = (2,0); draw(unitcircle); dot(O); dot(P); label('$P$', P, E); label('$C$', O, W); [/asy]$

Given a circle with center $C$ and a point $P$ that lies outside the circle, bisect circle $C$ with a second circle centered at $P$ .

$[asy] pair O = (0,0); pair P = (2,0); pair A = (0,1); pair B = (0, -1); draw(unitcircle); draw(A--B, red); draw(P--O, red); draw(circle(P, 2.24)); dot(O); dot(P); dot(A); dot(B); label('$P$', P, E); label('$C$', O, W); [/asy]$

Problem from class:

$[asy] import olympiad; import cse5; import geometry; size(150); defaultpen(fontsize(10pt)); defaultpen(0.8); dotfactor=4; pair X = origin; pair Y = (3,0); pair W = X+dir(120); pair Z = Y+dir(120); pair T = (0,2); pair S = T+dir(120); pair U = (3,2); pair V = U+dir(120); label("$X$",X,SW); label("$W$",W,SW); label("$T$",T,NE); label("$S$",S,NW); label("$Z$",Z,E); label("$Y$",Y,SE); label("$U$",U,E); label("$V$",V,NE); draw(X--Y); draw(Z--Y, dashed); draw(W--X, red); draw(X--Z, red); draw(Z--U, red); draw(Z--W,red); draw(U--X, red); draw(S--T--U--V--cycle); draw(X--T); draw(W--S); draw(Y--U); draw(Z--V,dashed); draw(W--U,red); [/asy]$

$[asy] unitsize(0.2 cm); pair A, B, E, P; A = (0,0); B = (8,0); E=(1,2); P = (B + reflect(A,(1,2))*(B))/2; draw((-10,0)--(10,0)); draw(A+(-1,-2)--8*E, red); draw(A--(0,25)); draw(B+-1*(1,2)--(9, 2)+7*(1,2), red); draw(B--P,dashed); dot("$A$", A, SE); dot("$B$", B, SE); dot("$P$", P, N); label("$8$", (A + B)/2, S); [/asy]$

[asy]

size(125); real ticklen=3; real tickspace=2;

real ticklength=0.1cm; real axisarrowsize=0.14cm; pen axispen=black+1.3bp; real vectorarrowsize=0.2cm; real tickdown=-0.5; real tickdownlength=-0.15inch; real tickdownbase=0.3; real wholetickdown=tickdown; void rr_cartesian_axes(real xleft, real xright, real ybottom, real ytop, real xstep=1, real ystep=1, bool useticks=false, bool complexplane=false, bool usegrid=true) {

   import graph;
   real i;
   if(complexplane) {
       label("",(xright,0),SE);
       label("",(0,ytop),NW);
   } else {
       label("",(xright+0.4,-0.5));
       label("",(-0.5,ytop+0.2));   
   }

   ylimits(ybottom,ytop);
   xlimits( xleft, xright);
   real[] TicksArrx,TicksArry;

   for(i=xleft+xstep; i<xright; i+=xstep) {
       if(abs(i) >0.1) {
           TicksArrx.push(i);
       }
   }
   for(i=ybottom+ystep; i<ytop; i+=ystep) {
       if(abs(i) >0.1) {
           TicksArry.push(i);
       }
   }

   if(usegrid) {
       xaxis(BottomTop(extend=false), Ticks("%", TicksArrx ,pTick=gray(0.72),extend=true),p=invisible);//,above=true);
       yaxis(LeftRight(extend=false),Ticks("%", TicksArry ,pTick=gray(0.72),extend=true), p=invisible);//,Arrows);
   }
   if(useticks) {
       xequals(0, ymin=ybottom, ymax=ytop, p=axispen, Ticks("%",TicksArry ,  pTick=black+0.8bp,Size=ticklength), above=true,  Arrows(size=axisarrowsize));
       yequals(0, xmin=xleft, xmax=xright, p=axispen, Ticks("%",TicksArrx ,  pTick=black+0.8bp,Size=ticklength), above=true,  Arrows(size=axisarrowsize));

   } else {
       xequals(0, ymin=ybottom, ymax=ytop, p=axispen,  above=true,  Arrows(size=axisarrowsize));
       yequals(0, xmin=xleft, xmax=xright, p=axispen,  above=true,  Arrows(size=axisarrowsize));
   }

}; rr_cartesian_axes(-5,5,-1,10); real f(real x) {return x*x;} real g(real x) {return 2*x*x;} draw(graph(f,-sqrt(10),sqrt(10),operator ..), red ,Arrows(size=axisarrowsize)); draw(graph(g,-sqrt(5),sqrt(5),operator ..), blue ,Arrows(size=axisarrowsize));

dot((2,4), p=orange); dot((2,8),p=orange); draw((2,4)--(2,8),p=orange, Arrow(size=2*axisarrowsize));

dot((-1,1), p=purple); dot((-1,2),p=purple); draw((-1,1)--(-1,2),p=purple, Arrow(size=2*axisarrowsize)); </asy>

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User:Jonjoseph