The radius is any line segment that joins the centre of a circle to its edge.

A pair of compasses is a tool which can be used to draw circles and arcs. A pair of compasses is sometimes referred to just as a compass.

Securing the skill of using a pair of compasses

Maths

Checking compass skills

Understanding constructing a circle

Constructing triangles

Constructing rhombi

Diagonals of a rhombus

Bisecting an angle

Perpendicular bisector of a line segment

Perpendicular to a given line through a given point

Problem solving with constructions

The constructions covered in this unit are built on in the future unit. In the future unit, pupils construct triangles and construct diagrams following specific restrictions.

The prior unit gave pupils the opportunity to explore polygons and begin to generalise their understanding of interior/exterior angles in regular polygons. In this unit, pupils will use the geometrical properties of a rhombus to perform various constructions. 

In this unit we develop skills in using a pair of compasses and ruler to construct various accurate shapes and angles including triangles, rhombi, perpendicular lines and angle bisectors.

Constructions

Lucas draws a circle with a pair of compasses. The image shows the pair of compasses just before he draws the circle. What is the radius of Lucas's circle?

The image shows two circles with points A and B at their centres. The distance from A to B is {{ }} cm.

Points A to D lie on a straight line. The radius of the large circle is 10 cm; the radius of the small circle is 6 cm. The distance from A to D is {{ }} cm.

The image shows a circle with centre at point A. Sofia draws a circle with radius 4 cm with its centre at point B. How many times will the two circles intersect?

Aisha draws two circles. One has a radius 5 cm, the other has a radius 9 cm. The distance between the centre points of each circle is 14 cm. Which image matches Aisha's drawings?

In which image is the radius labelled with a question mark?

An {{ }} of a circle is part of the circle’s circumference.

Points A and B are {{ }} from a third point C if AC = BC. 

The radius of a circle is 18 cm. The diameter of the circle is {{ }} cm.

In which image would the pair of compasses draw a circle with a diameter of 6 cm.

Alex draws a circle with a pair of compasses. The image shows the pair of compasses just before he draws the circle. What is the circumference of Alex's circle?

Securing the skill of using a pair of compasses

Lesson outcome