11.3: Geometrical constructions of triangles and quadrilaterals

1) Lesson Objectives:

You should be able to

• Construct triangles

• Construct quadrilaterals

Terminologies

• Construction arcs

A: Introduction to geometrical constructions

Read and try to understand Textbook 1B explanations and worked examples: pg 114 to 115.

Tools used in constructions:

• protractor

• compass

• ruler

• set square (Another tool for drawing parallel lines)

IMPORTANT: Always leave all construction arcs in the construction. The arcs are the method marks for constructions questions. DO NOT erase the construction arcs

B: Constructions of Triangles

Read and try to understand Textbook 1B explanations and worked examples: pg 116 to 118.

Do watch all the videos to learn how to construct triangles.

C: Constructions of Quadrilaterals

Read and try to understand Textbook 1B explanations and worked examples: pg 119 to 120.

Do watch all the videos to learn how to construct quadrilaterals.

Construction of Parallel Lines, Angle Bisector and Perpendicular Bisector

Possible question type on perpendicular bisectors:

• Construct the perpendicular bisector for line AB

(Note: Use compass and follow the steps in the video )

• The point P is equidistant from A and B.

(Note: Must construct the perpendicular bisector first. Then point P will be any point on the perpendicular bisector drawn.)

Possible questions type on angle bisectors:

• Construct the angle bisector for angle PQR.

(Note: Use compass and follow the steps in the video )

• The point Y is equidistant from PQ and QR.

(Note: Must construct the angle bisector first. Then point Y will be any point on the angle bisector drawn.)

Additional Videos on constructions