\documentclass[border=1mm]{standalone} \usepackage{luamplib} \begin{document} \mplibtextextlabel{enable} \begin{mplibcode} vardef radical_axis(expr ca, cb) = numeric t, d, ra, rb; ra = abs(center ca - point 0 of ca); rb = abs(center cb - point 0 of cb); d = abs(center cb - center ca); 2t = 1 + (ra+rb) / d * (ra-rb) / d; (up -- down) scaled 89 rotated angle (center cb - center ca) shifted t[center ca, center cb] enddef; input tangent-times vardef invert_point(expr P, o, r) = save p, d; pair p; numeric d; p = P - o; d = abs p; if d > 0: o + unitvector p scaled (r/d*r) else: errmessage("Inversion undefined at center.") fi enddef; vardef pole(expr Line, Circle) = save p, o, r; pair o, p; numeric r; o = center Circle; r = 1/2 abs (point 4 of Circle - point 0 of Circle); p = whatever [point 1 of Line, point 0 of Line]; p - o = whatever * direction 0 of Line rotated 90; invert_point(p, o, r) enddef; vardef polex(expr a, b, o, r) = save p; pair p; p = whatever [a, b]; p - o = whatever * (a-b) rotated 90; invert_point(p, o, r) enddef; vardef three_point_circle(expr a,b,c) = save m; pair m; m = whatever [a,b] rotatedaround(.5[a,b],90) = whatever [b,c] rotatedaround(.5[b,c],90); fullcircle scaled 2 length(m-a) shifted m enddef; vardef through(expr a, b, o) = save d; numeric d; d = abs(a-b); (1+o/d)[b, a] -- (1+o/d)[a, b] enddef; beginfig(1); path c[]; numeric r[]; z1 = origin; r1 = 101; z2 = 233 right rotated 4; r2 = 53; z3 = 209 right rotated -42; r3 = 31; forsuffixes $=1, 2, 3: c$ = fullcircle scaled 2 r$ shifted z$; endfor pair ecs[], ics[]; for i=1 upto 3: numeric j, k; j = i mod 3 + 1; k = 10i + j; ics[k] = (r[i]/(r[i]+r[j]))[z[i], z[j]]; ecs[k] = (r[i]/(r[i]-r[j]))[z[i], z[j]]; endfor path a[]; a1 = radical_axis(c1, c2); a2 = radical_axis(c2, c3); a3 = radical_axis(c3, c1); z0 = whatever [point 0 of a1, point 1 of a1] = whatever [point 0 of a2, point 1 of a2]; z11 = polex(ecs31, ecs12, z1, r1); z21 = polex(ecs31, ecs12, z2, r2); z31 = polex(ecs31, ecs12, z3, r3); z12 = c1 intersectionpoint (z0 -- z11); z22 = c2 intersectionpoint (z0 -- z21); z32 = c3 intersectionpoint (z0 -- z31); z13 = c1 intersectionpoint (z11 -- 8[z0,z11]); z23 = c2 intersectionpoint (z21 -- 8[z0,z21]); z33 = c3 intersectionpoint (z31 -- 8[z0,z31]); z14 = whatever[ecs12, ecs31] = whatever[z1, z11]; z24 = whatever[ecs12, ecs31] = whatever[z2, z21]; z34 = whatever[ecs12, ecs31] = whatever[z3, z31]; drawoptions(withcolor 3/4[blue, white]); draw c1; draw c2; draw c3; drawoptions(withcolor 1/4[blue, white]); label.urt(btex $C_1$ etex, point 1 of c1); label.top(btex $C_2$ etex, point 2 of c2); label.rt (btex $C_3$ etex, point 1/2 of c3); draw ecs12 -- ecs31 -- ecs23; drawoptions(withpen pencircle scaled 1/4 withcolor 3/4[2/3 blue, white]); draw a1; draw a2; draw a3; draw through(z1, z14, 6); draw through(z2, z24, 6); draw through(z3, z34, 6); drawoptions(withpen pencircle scaled 1/4 withcolor 1/2 white); draw through(z0, z13, 6); draw through(z0, z23, 6); draw through(z0, z33, 6); drawoptions(withcolor 1/256(203, 92, 13)); drawdot z0 withpen pencircle scaled 3/2 dotlabeldiam; z99 = z0 shifted 24 dir -6; label.rt("\vbox{\openup-4pt\halign{\hss #\hss\cr Radical\cr centre\cr}}", z99); interim ahangle := 20; drawarrow z99 -- z0 cutafter fullcircle scaled 16 shifted z0 withpen pencircle scaled 1/3; drawoptions(withcolor 1/256(239, 114, 21)); dotlabel.urt("\small Pole", z11); dotlabel.ulft("\small Pole", z21); dotlabel.urt("\small Pole", z31); drawoptions(withcolor 2/3 red); draw three_point_circle(z12, z22, z32); draw three_point_circle(z13, z23, z33); drawdot z12 withpen pencircle scaled 3/4 dotlabeldiam; drawdot z22 withpen pencircle scaled 3/4 dotlabeldiam; drawdot z32 withpen pencircle scaled 3/4 dotlabeldiam; drawdot z13 withpen pencircle scaled 3/4 dotlabeldiam; drawdot z23 withpen pencircle scaled 3/4 dotlabeldiam; drawdot z33 withpen pencircle scaled 3/4 dotlabeldiam; drawoptions(withcolor 1/2[blue, white]); drawdot z1 withpen pencircle scaled dotlabeldiam; drawdot z2 withpen pencircle scaled dotlabeldiam; drawdot z3 withpen pencircle scaled dotlabeldiam; drawdot z14 withpen pencircle scaled dotlabeldiam; drawdot z24 withpen pencircle scaled dotlabeldiam; drawdot z34 withpen pencircle scaled dotlabeldiam; draw thelabel.top(btex Axis of similitude, as polar etex, origin) rotated angle (ecs12 - ecs31) shifted 3/4[ecs31, ecs12]; drawoptions(); endfig; \end{mplibcode} \end{document}