7.2 special triangles

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7.2 triangles

tri  means three

angle means angle

together triangle

triangles

The angles of a

triangle together are

always 180°

There are 3 types of special triangles:

special triangle 1

isosceles triangle

- two legs of the same length and one base

- two base angles and one vertex angle

- two angles with the same degree

which side is the base

A

AB

B

BC

C

AC

D

special triangle 2

equilateral triangle

- all angles are the same size

- all sides are the same length 

how many degrees is each angle

A

45

B

60

C

90

D

180

special triangle 3

right-angled triangle

- has 1 angle of 90°

right angled isosceles triangle

- right angle

- two legs of the same length

-

a 90° angle

2 legs of the same length

all angles are of the same degree

has a base

Homework

Do exercises 11, 12, 13 and 14 (p.54)