MathDB

91

Part of 1988 IMO Longlists

Problems(1)

A regular 14-gon with side a is inscribed in a circle

Source: IMO LongList 1988, Vietnam 3, Problem 91 of ILL

11/9/2005
A regular 14-gon with side aa is inscribed in a circle of radius one. Prove 2−a2⋅a>3⋅cos⁡(π7). \frac{2-a}{2 \cdot a} > \sqrt{3 \cdot \cos \left( \frac{\pi}{7} \right)}.
trigonometrygeometry unsolvedgeometry