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Constructions and loci questions require students to use a compass and straightedge to construct perpendicular bisectors, angle bisectors and loci. These questions test precision and understanding of geometric properties.
Students make these errors again and again. Knowing them in advance gives you a head start.
Rubbing out construction arcs (they must be left visible for marks)
Setting the compass to the wrong width
Not keeping the compass width consistent throughout the construction
Insights pulled from Cambridge IGCSE (0580) examiner reports — the exact mistakes candidates make every year.
For similar shapes: area scale factor = (linear scale factor)², volume scale factor = (linear)³. If lengths are doubled, areas are × 4 and volumes are × 8 — not × 2.
Source: CIE 0580 · Feb/March 2024 · Paper 4 · Q2c(ii)
Circle theorem reasons must be exact: 'opposite ANGLES of a cyclic quadrilateral add to 180°' (not 'sides'). Use the precise syllabus vocabulary — 'linear pair' is NOT the CIE phrase.
Source: CIE 0580 · Feb/March 2024 · Paper 4 · Q2a
At each vertex of a polygon, interior angle + exterior angle = 180° (they form a straight line). It's the SUM of all exterior angles that equals 360°, not one pair.
Source: CIE 0580 · Feb/March 2023 · Paper 2 · Q12
Based on 3of 500+ insights extracted from CIE 0580 examiner reports (2018–2024).
This topic appears in the Cambridge IGCSE past papers. Our AI tutor can help with it on any question.
Useful for this topic:
Angle facts are fundamental to geometry and regularly appear across all papers. Students must apply rules about angles on straight lines, at points, in triangles, in parallel lines and in polygons to find missing angles with clear reasoning.
Area and perimeter calculations cover rectangles, triangles, parallelograms, trapezia and circles. Compound shapes combine these, and questions can involve sectors and segments of circles.
Pythagoras' theorem relates the three sides of a right-angled triangle and is one of the most practical geometry topics at Cambridge IGCSE. It is used in 2D and 3D problems, coordinate geometry, and combined with trigonometry.
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Draw and label geometric figures as you revise