<Tri-2026-2351>, hint

Let F on BD such that CB=CF, then ABC and CBF are similar,

CEF is equilateral.  CDF is isosceles  <FCD=<FDC=40, FDE is isosceles  FD=FE

<DFE=180-60-80=40. Hence <EDC=<EDF-<CDF=70-40=30

<

<Tri-2026-2351> isosceles, angle

<Spain MO 1987>

 

<Tri-2026-2350>, hint

 

<Tri-2026-2350>, general, construction

<Spain MO 1983>

r: radius of incircle given

<Qua-2026-826>, hint