George Baloglou and Michel Helfgott, Angles, area, and perimeter caught in a cubic,
Forum Geometricorum, 8 (2008) 13--25.

Abstract. The main goal of this paper is to establish sharp bounds for the angles and for the side ratios of any triangle of known area and perimeter. Our work is also related to the well known isoperimetric inequality.

[ps file][pdf]