The sum of the angles in a triangle is always 180 degrees. This fundamental property of triangles is applicable in Euclidean geometry, which deals with flat surfaces and includes various types of triangles, such as equilateral, isosceles, and scalene. Regardless of the triangle's shape or size, this rule holds true and is essential for solving many geometrical problems. Understanding this concept is crucial as it relates to various applications in mathematics, architecture, and physics. The 180-degree property of triangles also serves as a basis for exploring more complex geometric figures and relationships.