olymmath

CGMO 2012 Problem 2

    Circles Q1Q_1 and Q2Q_2 are tangent to each other externally at TT . Points AA and EE are on Q1Q_1 , lines ABAB and DEDE are tangent to Q2Q_2 at BB and DD , respectively, lines AEAE and BDBD meet at point PP . Prove that (1) ABAT=EDET\frac{AB}{AT}=\frac{ED}{ET} ; (2) ∠ATP+∠ETP=180∘\angle ATP + \angle ETP = 180^{\circ} .

    import graph; size(5.97cm); real lsf=0.5; pathpen=linewidth(0.7); pointpen=black; pen fp=fontsize(10); pointfontpen=fp; real xmin=-6,xmax=5.94,ymin=-3.19,ymax=3.43;
    pair Q_1=(-2.5,-0.5), T=(-1.5,-0.5), Q_2=(0.5,-0.5), A=(-2.09,0.41), B=(-0.42,1.28), D=(-0.2,-2.37), P=(-0.52,2.96);
    D(CR(Q_1,1)); D(CR(Q_2,2)); D(A--B); D((-3.13,-1.27)--D); D(P--(-3.13,-1.27)); D(P--D); D(T--(-3.13,-1.27)); D(T--A); D(T--P);
    D(Q_1); MP("Q_1",(-2.46,-0.44),NE*lsf); D(T); MP("T",(-1.46,-0.44),NE*lsf); D(Q_2); MP("Q_2",(0.54,-0.44),NE*lsf); D(A); MP("A",(-2.22,0.58),NE*lsf); D(B); MP("B",(-0.35,1.45),NE*lsf); D((-3.13,-1.27)); MP("E",(-3.52,-1.62),NE*lsf); D(D); MP("D",(-0.17,-2.31),NE*lsf); D(P); MP("P",(-0.47,3.02),NE*lsf);
    clip((xmin,ymin)--(xmin,ymax)--(xmax,ymax)--(xmax,ymin)--cycle);

    Dataset text AI-MO AoPS. Quoted with source.

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