Constructions — O/L Mathematics

What must I remember about Constructions?

• Geometric constructions require strictly a pair of compasses and an unmarked straight edge; all construction arcs must remain clearly visible.
• Perpendicular bisector of a line segment AB: Draw intersecting arcs of radius > (1/2)AB from A and B; the line through intersection points bisects AB at 90°.
• Angle bisector: From vertex, strike an arc across both arms; from intersection points, strike equal arcs; the ray through their intersection bisects the angle.
• Standard angle constructions: 60° (equilateral triangle principle), 30° (bisect 60°), 90° (bisect 180° straight angle or perpendicular bisector), 45° (bisect 90°).
• Triangle circumcentre (intersection of perpendicular bisectors of sides) and incentre (intersection of internal angle bisectors).

Test yourself (1 minute)

1. Never erase construction arcs

   Erasing construction arcs forfeits all method marks in Paper 2 Part B geometric construction questions.

2. Compass sharpness

   Ensure compass pencil is razor-sharp; double-lines, fuzzy arcs, or blunt impressions incur accuracy penalties.

3. Measurements validation

   Measure the constructed lengths and angles with ruler/protractor and write the values down clearly when requested in sub-questions.

Practise Constructions questions today

Source: NIE G.C.E. (O/L) Mathematics Syllabus (Grade 10 & 11, Unit 27/23)

What should I study first?

What comes next?

Next in the syllabus

Where does Constructions fit in the syllabus?

Grade 10 · Term 3 · Grade 11 · Term 3