Compass constructionsBisect a segment
Name: Date:
Construct each perpendicular bisector. Leave your arcs showing.
1Construct the bisector of AB.
2Construct the bisector of AB.
3Construct the bisector of AB.
4Construct the bisector of AB.
Perpendicular bisector worksheets
Two equal arcs, one from each end, crossing above and below — and the line through those crossings cuts the segment exactly in half, at exactly a right angle. One construction, two results, and no measuring at any point.
If they get stuck
Perpendicular bisector
The answer key prints on a separate page.
What's on this sheet
Open the compass to more than half of AB and swing arcs from A above and below the segment; keeping the same opening, do it again from B. The two pairs cross at two points, and the line through them is the perpendicular bisector. It works because every point on it is the same distance from A as from B — which is what the equal openings guarantee.
Why this sheet works
The one condition is the opening: more than half of AB, or the arcs never meet. Children find this out by trying it, which is worth more than being told, so the sheets leave room above and below each segment for arcs of any workable size. Segments are printed at true size in whole millimetres so a ruler check reads a round number.
How this one works
One question off this sheet, worked a step at a time — with a sentence saying what just happened and why.
Perpendicular bisector, step by step