# Constructions and Loci

Students learn how to construct angle and line bisectors using a pair of compasses.  Later, students apply this knowledge to solve problems involving loci about a point and line.  This unit takes place in   Year 9 Term 6.

##### Revision Lessons

Prerequisite Knowledge

• Identify and construct a radius, diameter, circumference, area, chord, tangent and arc.
• Measure and begin to record lengths and heights
• Identify acute and obtuse angles and compare and order angles up to two right angles by size

Prerequisite Knowledge

• Identify and construct a radius, diameter, circumference, area, chord, tangent and arc.
• Measure and begin to record lengths and heights
• Identify acute and obtuse angles and compare and order angles up to two right angles by size

Key Concepts

• It is important for students to sketch the diagram before attempting their construction. The sketch should be drawn freehand and contain all the necessary information.
• Bisectors are used to half an angle as well as a length of a line segment.
• Constructing a 60° angle using a pair of compasses is an essential skills throughout this topic as it goes on to equilateral triangles and reflex angles.

Common Misconceptions

• Students often have difficulty constructing smooth arcs using a pair of compasses. Encourage them to try different techniques such as rotating the paper rather than the compasses.
• It is important to leave in construction lines as these form the working out.

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