In any triangle, the sum of the interior angles always equals 180 degrees. This rule holds true for all types of triangles, whether they are scalene, isosceles, or equilateral.
To understand why this is the case, you can visualize or even draw a triangle and then extend one of its sides. By doing so, you’ll create alternate interior angles and straight angles that show how the original angles interact. The concept can be further demonstrated using various geometrical proofs, which confirm that no matter how you configure the triangle, the total will consistently sum up to 180 degrees.
This fundamental property of triangles is a cornerstone in geometry and underpins many other principles and theorems in the subject.