Loci and construction
Loci: paths of points satisfying a rule. Construction: angle bisector, perpendicular bisector with compass.
Both tiers cover four standard constructions: perpendicular bisector of a line; angle bisector; perpendicular from a point to a line; perpendicular at a point on a line. Loci include the path of points equidistant from a line, point or pair of points.
Worked examples
Locus of points 3 cm from A: a circle radius 3 cm centred on A.
Locus equidistant from two lines: the angle bisector.
Locus equidistant from two points: the perpendicular bisector of the line joining them.
Frequently asked questions
Pencil arcs only?
Compass arcs must be visible in the construction (not erased). Marks are awarded for correct construction lines as well as final answer.
Bisecting an angle?
Same compass radius from the angle vertex; arcs cross both sides; use those crossings as new centres for two more arcs that intersect; draw the bisector.