Page 59 - Key Stage 3 Geometry

You will notice the setsquares in your Helix box are

right-angled triangles, one of them being an isosceles
right-angled triangle. Whatever shape triangle you

o
have the internal angles will always add up to 180 .
The equilateral triangle has three internal angles of
o
60 and the isosceles triangles have two internal
angles which are the same. The right-angled triangle
o
as the name suggests has one internal 90 angle.

Whatever shape triangle you have it can be converted

into two right angled triangles by dropping a
perpendicular line as illustrated in the diagram below.

Irregular triangle Two right angled
triangles

Exercise 4.1

Measuring the angles in an irregular triangle. Do the

following.

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