In geometry, what is the sum of the interior angles of a triangle?

The sum of the interior angles of a triangle is always 180 degrees, regardless of the type of triangle (whether it is scalene, isosceles, or equilateral). This property is foundational in Euclidean geometry and can be visualized by drawing a triangle and extending one of its sides. If you then draw a line parallel to one side of the triangle through the opposite vertex, you create two alternate interior angles that, together with the other angle, complete a straight line. Since a straight line is 180 degrees, this confirms that the total measures of the triangle's three angles add up to 180 degrees. This principle is essential in various geometric proofs and theorems, reaffirming its importance in mathematics. Thus, the correct answer aligns with this established geometric fact.