What is the sum of the angles in a triangle?

The sum of the angles in a triangle is universally known to be 180 degrees. This is a fundamental property in Euclidean geometry, which states that regardless of the type of triangle—whether it is scalene, isosceles, or equilateral—the internal angles will always add up to 180 degrees.

To understand this concept more deeply, consider a triangle formed by connecting three points in a plane. By drawing lines to these points from a vertex, one can visualize how the angles formed at each vertex contribute to the total. The property holds true regardless of the triangle's shape or size.

This characteristic plays a crucial role in various geometric proofs and is essential for solving many problems related to triangles, including those involving determining missing angles when given one or two angles. The other options represent angles or sums that do not apply to triangles, as 90 degrees pertains to a right angle, while 270 and 360 degrees pertain to full rotational measures in circles, which do not relate to the properties of triangles.