Acute and obtuse triangles "x", then If two obtuse triangles have sides ("a, b, c") and ("p, q, r") with "c" and "r" being the respective longest sides, then The Calabi triangle, which is the only non-equilateral triangle for which the largest square that fits in the interior can be positioned in any of three different ways, is obtuse and isosceles with base angles 39.1320261...° and third angle 101.7359477...°. The equilateral triangle, with three 60° angles, is acute. The Morley triangle, formed from any triangle by the intersections of its adjacent angle trisectors, is equilateral and hence acute. The golden triangle is the isosceles
Circle packing in an equilateral triangle removing any single circle from the optimal hexagonal packing of circles. This conjecture is now known to be true for . Minimum solutions for the side length of the triangle: A closely related problem is to cover the equilateral triangle with a fixed number of equal circles, having as small a radius as possible. Circle packing in an equilateral triangle Circle packing in an equilateral triangle is a packing problem in discrete mathematics where the objective is to pack "n" unit circles into the smallest possible equilateral triangle. Optimal solutions are known for "n" < 13 and for any triangular