35

Part of 1982 IMO Longlists

Problems(1)

The radius is half of circumradius-->triangle is equilateral

Source: IMO LongList 1982 - P35

If the inradius of a triangle is half of its circumradius, prove that the triangle is equilateral.

geometrycircumcircleinradiustrigonometrygeometric transformationhomothetyinequalities