Shape and Space

CONSTRUCTION

STRONG TRIANGLES

Triangles are very important.

Shapes that are made from

triangles are usually very strong.

Many structures like bridges,

pylons and towers are built

using triangles.

DRAWING A TRIANGLE

Draw triangle ABC

AB = 7cm,

Angle A = 36°

Angle B = 58°

36° 58°

7cmA B

C

What size is angle C?36 + 58 = 94°

Angle C = 180 – 94 = 86°

Or you could measure angle C using the protractor

EXERCISES

1. Draw Triangle LMNa) LM = 8cm,

Angle L = 47°Angle M = 32°

b) What is angle N?

2. Draw Triangle PQRa) PQ = 6cm,

Angle P = 28°Angle Q = 78°

b) What is angle R?

3. Draw Triangle XYZa) XY = 6.5cm

Angle X = 56°Angle Y = 43°

b) Beth yw ongl Z?

BISECT AN ANGLE

It’s possible to bisect an angle (in half) using a compass.

Step 1 : Open the compassto any distance. You mustkeep the compass at this distance.

BISECT AN ANGLE

It’s possible to bisect an angle (in half) using a compass.

A

B

Step 2 : Put the compass onthe corner of the angle and draw a small arc which crossboth arms of the angle. Label these points A and B.

BISECT AN ANGLE

It’s possible to bisect an angle (in half) using a compass.

A

B

Step 3 : Put the compass onpoint A and repeat step 2.Then do the same with point B.

BISECT AN ANGLE

It’s possible to use the same method to draw a perfectcircle within a triangle.

Notice that the circletouches the threesides of the triangle.

REMEMBER TO KEEP THE COMPASS AT THE SAME DISTANCE

BISECT AN ANGLE

REMEMBER TO KEEP THE COMPASS AT THE SAME DISTANCE