This introduction covers The 180° Rule 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 1 of 9 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
The 180° Rule
Every triangle in the universe has angles that add up to exactly 180°. It doesn't matter if it's tiny or massive, flat or tilted - the three angles ALWAYS sum to 180°. This is the most important triangle fact you'll ever learn!
Visual: Types of Triangles
Tip: Equal sides have matching tick marks, equal angles have matching arcs
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