How_To_Be_Good_At_Math

GEOMETRY • TRIANGLES 215

Right-angled

triangle

Two of the sides meet to

make a right angle (90°).

Learn more about right

angles on page 232.

Isosceles triangle

Two sides of the

triangle are the same

length, and the two

Opposite angles

equal sides are the

same size.

Scalene triangle

The three sides are

all different lengths, and

none of the angles are

the same.

Equilateral triangle

All three sides are

the same length and the

three angles are the

same size.

TRY IT OUT

Triangle test

This picture contains

different kinds of

triangles. Can you spot

an equilateral, an

isosceles, a scalene, and

a right-angled triangle?

Answers on page 320

Types of angle

We give triangles different names depending on the lengths of their

sides and the sizes of their angles. On pages 240-41, you’ll find out

in a polygon Calculating the angles

Dashes

show sides

are equal

Corner

symbol shows

Right angles

Curved lines

(arcs) mark

equal angles

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