Geometry & MeasuresStudy Notes

Common Mistakes

Part of Properties of Triangles · GCSE GCSE Mathematics revision

This study notes covers Common Mistakes 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 7 of 9 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 7 of 9

Practice

12 questions

Recall

3 flashcards

Common Mistakes

✗ Wrong: Assuming all isosceles triangles have angles of 45°, 45°, 90°

✓ Right: Isosceles just means 2 equal sides/angles - the actual angles vary

✗ Wrong: Exterior angle = 180° − interior angle at same vertex

✓ Right: That IS true, but the quicker method is: exterior = sum of OTHER two interior angles

Keep building this topic

Read this section alongside the surrounding pages in Properties of Triangles. That gives you the full topic sequence instead of a single isolated revision point.

Worked Example 3: Exterior Angle Practice Questions The 180° Rule Types of Triangles

Practice Questions for Properties of Triangles

What is the sum of the interior angles of any triangle?

A. 90°
B. 180°
C. 270°
D. 360°

1 markfoundation

Describe the key properties of an equilateral triangle. State two properties relating to sides and two relating to angles.

2 marksstandard

Quick Recall Flashcards

Triangle Angle Sum

Always 180°

Isosceles Triangle

Two equal sides, two equal angles

12 questions on Properties of Triangles — practise free

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Worked Example 3: Exterior Angle

Practice Questions