An obtuse triangle is a type of triangle that has one angle measuring more than 90 degrees. This means that the largest angle in the triangle is obtuse, while the other two angles are acute, each measuring less than 90 degrees. The sides of an obtuse triangle can vary in length, but the longest side is always opposite the obtuse angle. Obtuse triangles can be classified into different types based on the lengths of their sides. For example, an obtuse triangle can be isosceles, where two sides are of equal length, or scalene, where all sides are of different lengths. Understanding the properties of obtuse triangles is important in geometry and various applications.