Mathematics and English progression

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Step 7 Objective

Use a straight edge and compasses to construct:

• the midpoint and perpendicular bisector of a line segment;
• the bisector of an angle;
• the perpendicular from a point to a line;
• the perpendicular from a point on a line.

Construct a triangle, given three sides (SSS); use ICT to explore these constructions.

Examples of what pupils should know and be able to do

• Construction of triangle using compasses - Rtf (rich text format) document (16Kb)

• Construction using properties of shape - Rtf (rich text format) document (1.3Mb)

• FTM(S)Y789 pp. 221-223 - Acrobat pdf document (64Kb)

Probing questions

Why are compasses important when doing constructions?

Why does understanding the properties of a rhombus help you to understand simple constructions such as the bisector of an angle?

For which constructions is it important to keep the same compass arc (distance between the pencil and the point of your compasses)?

Why?

What if pupils find this a barrier?

Give pupils, in pairs, simple constructions to study, discuss and copy, using a straight edge and compasses only. (Those in FTM(S)Y789 p. 221 - Acrobat pdf document (56Kb) are the target - but ones based on hexagons also help pupils to get a feeling for using arc lengths.)

TL4Y7: Shape, space and measures 3: S3.1 - Acrobat pdf document (44Kb) might be useful for pupils who have difficulties with constructing triangles.