Triangle Angle Sum Theorem

Discover why the interior angles of every triangle always add up to exactly 180°.

The Fundamental Rule

Angle A + Angle B + Angle C = 180°

The sum of interior angles in ANY triangle is always exactly 180 degrees

Works for all triangles - scalene, isosceles, equilateral

Always exactly 180°, never more, never less

True in all geometries and mathematical systems

Practice angle sum with isosceles triangles. Input one angle and see how the theorem determines the other angles automatically.

Test your understanding of angle relationships and triangle properties.