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trisecting sides + constructing similar triangles - Austrian-Polish 2003

Source:

May 18, 2019
geometrysimilar trianglesSegment

Problem Statement

ABCABC is a triangle. Take a=BCa = BC etc as usual. Take points T1,T2T_1, T_2 on the side ABAB so that AT1=T1T2=T2BAT_1 = T_1T_2 = T_2B. Similarly, take points T3,T4T_3, T_4 on the side BC so that BT3=T3T4=T4CBT_3 = T_3T_4 = T_4C, and points T5,T6T_5, T_6 on the side CACA so that CT5=T5T6=T6ACT_5 = T_5T_6 = T_6A. Show that if a=BT5,b=CT1,c=AT3a' = BT_5, b' = CT_1, c'=AT_3, then there is a triangle ABCA'B'C' with sides a,b,ca', b', c' (a=BCa' = B'C' etc). In the same way we take points TiT_i' on the sides of ABCA'B'C' and put a=BT6,b=CT2,c=AT4a'' = B'T_6', b'' = C'T_2', c'' = A'T_4'. Show that there is a triangle ABCA'' B'' C'' with sides ab,ca'' b'' , c'' and that it is similar to ABCABC. Find a/aa'' /a.