2.7 – Triangles

Type of ∆ Definition Picture

Equilateral Triangle

CLA

SSIF

ICAT

ION

BY

SID

ES

All sides are ≅

Type of ∆ Definition Picture

Isosceles Triangle

CLA

SSIF

ICAT

ION

BY

SID

ES

2 Sides ≅base

leg leg

Type of ∆ Definition Picture

Scalene Triangle

CLA

SSIF

ICAT

ION

BY

SID

ES

No sides are ≅

Type of ∆ Definition Picture

EquiangularTriangle

CL

ASS

IFIC

ATIO

N B

Y A

NG

LE

S

All angles are ≅

Type of ∆ Definition Picture

Acute Triangle

CLA

SSIF

ICAT

ION

BY

AN

GLE

S

All angles are acute

Type of ∆ Definition Picture

Right Triangle

CLA

SSIF

ICAT

ION

BY

AN

GLE

S

One right angle

leg

leghyp

otenuse

Type of ∆ Definition Picture

Obtuse Triangle

CLA

SSIF

ICAT

ION

BY

AN

GLE

S

One obtuse angle and 2 acute angles

Classify the triangle by the best definition based on sides and angles. Then find the sum of the interior angles.

scaleneright180

equilateralequiangular

180

isoscelesobtuse180

4. The sum of ANY triangles interior angles is 180°. Use this fact to solve for x below.

x + 75 + 54 = 180x + 129 = 180

x = 51

2x + 3x + 55 = 1805x + 55 = 180

x = 255x = 125

4x – 1 + 3x + 90 = 1807x + 89 = 180

x = 137x = 91

A = 30 un2

A = ½(12)(5)

A = 30 un2

A = ½(12)(5) A = 30 un2

A = ½(12)(5)

b

h

b

h

Triangle:

Picture Perimeter Area

TriangleAdd the 3 sides

2bhA

12

A bh

30 16 34P 80P in

1 30 162

A

2240A in

12

A bh

20 48 39P 107P cm

1 48 152

A

2360A cm

12

A bh

7 13 10P 30P m

1 10 52

A

225A m

12

A bh

4. If the area of the triangle is 63cm2, find the height of the triangle.

12

A bh

163 212

h

126 21h6cm h