Use the standard ruler and compass constructions
- perpendicular bisector of a line segment
- constructing a perpendicular to a given line from a given point
- constructing a perpendicular to a given line at a given point
- bisecting a given angle
Note that all these Math Open Reference demonstrations are available as a printable atep by step instruction sheet, see for example the guide to bisecting an angle.
The AQA specification also includes a note that Constructing a 60° angle is required. This is shown here by constructing an equlateral triabgle.
Students will be asked to use these constructions to construct given figures and solve loci problems. Students should also know that the perpendicular distance from a point to a line is the shortest distance to the line.
The constructions shown here are all from the excellent Math Open Reference by John Page. (There are many more constructions given on the site which are not a GCSE requirement). Another very useful source for demonstrations comes from BBC Bitesize on Loci and Constructions which gives step by step diagrams and instructions.
The BBC site also has clear examples of solving problems using constructions.