Chapter 11 Constructions

Notes

Constructions:

Drawing geometrical figures accurately

Uses compass and ruler

Important instruments:

Compass

Scale

Pencil

Protractor

Basic constructions:

Line segment

Angle

Triangle

Circle

Tangent

Important concepts:

Perpendicular bisector

Divides line into equal parts

Makes 90° angle

Angle bisector

Divides angle into two equal angles

Tangent construction

Tangent always perpendicular to radius

Triangle constructions:

SSS

SAS

ASA

Similar triangle construction:

Uses proportional division

Important points:

Keep compass radius fixed carefully

Draw neat diagrams

Use sharp pencil

Common mistakes:

Wrong compass opening

Improper measurements

Untidy arcs

Wrong angle marking