This key facts covers Triangle Angle Rules within Properties of Triangles for GCSE Mathematics. Revise Properties of Triangles in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 3 of 9 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Triangle Angle Rules
| Rule | Description |
|---|---|
| Interior angles sum | Always add up to 180° |
| Exterior angle | Equals the sum of the two opposite interior angles |
| Isosceles base angles | The two angles opposite the equal sides are equal |
Practice questions for Properties of Triangles
What is the sum of the interior angles of any triangle?
Describe the key properties of an equilateral triangle. State two properties relating to sides and two relating to angles.
Quick recall flashcards
Triangle Angle Sum
Always 180°
Isosceles Triangle
Two equal sides, two equal angles