What name is given to a triangle in which two sides are equal in length?
Isosceles triangle of recognition of the concept of "betweenness" and the resulting ambiguity of "inside" versus "outside" of figures. Isosceles triangle In geometry, an isosceles triangle is a triangle that has two sides of equal length. Sometimes it is specified as having "exactly" two sides of equal length, and sometimes as having "at least" two sides of equal length, the latter version thus including the equilateral triangle as a special case. Examples of isosceles triangles include the isosceles right triangle, the golden triangle, and the faces of bipyramids and certain Catalan solids. The mathematical study of isosceles triangles dates back to ancient
Triangle of the lengths of any two sides of a triangle must be greater than or equal to the length of the third side. That sum can equal the length of the third side only in the case of a degenerate triangle, one with collinear vertices. It is not possible for that sum to be less than the length of the third side. A triangle with three given positive side lengths exists if and only if those side lengths satisfy the triangle inequality. Three given angles form a non-degenerate triangle (and indeed an infinitude of them) if and only if both