GLORY TWINKLE IX E

Anggun Nugraha OktavianiDeti Nur KarinaFiona SalfadillaRifda Nadifah

Umroh Indah Lestari

CONE

CONE

The

defi

nitio

n

The

elem

ents

The net The examples in daily life

The form

ulas

The exam

ple of

question

CONE

In geometry, the cone is a special pyramidbased circle. Cone has 2 sides, 1 angle point

and 1 edge. Side of the upright cone is not a triangle but in the form of curved cone called a curved surface or lateral area.A cone consist of the base circle shaped and the

blanket sector shaped.

The Elements of Cone

h

r

ll

r

2 ∏r

2 ∏ lC=2 ∏ rC=

Area of Circle∏ l 2

2rB=∏

B = Base area of circleC = Circumference of circleh = height of coner = radius of circlel = slant height of cone

The Net of Cone

The example of cones in daily life

CONES

TRAFFIC CONE

ANAK KRAKATAU MOUNTAIN

The Formula of Cone Lateral Area / Curved Surface :

=area of sectorarea of circle

Perimeter of sector / perimeter of cone’s base perimeter of circle

=area of sector

∏ l 2

2 r∏

2∏ l 2

r=

area of sector∏ l 2 l

∏ l 2

∏ l 2

∏ r lArea of sector =

h

r

ll

r

2 ∏r

2 ∏ lC=2 ∏ rC=

Area of Circle∏ l 2

2rB=∏

Total Surface Area :T = Area of sector + Area of cone’s baseT = Cs + BaT = (∏ r l) + (∏ r2 )

Volume Of Cone :

V = Ba . h

V = (∏ r2 ) h

Example

h = 12cm

r = 5cm

A cone has a base diameter of 10 cm and height of 12 cm. For ∏ = 3.14Find : a. the curved surface area b. the base area c. the surface area d. the volume

SolutionGiven that : r = 5 cm

h = 12 cm

∏ = 3. 14

l 2 = h2 + r 2

l = l = l =

l = l = 13 cm

So, the slant height of cone is 13 cm.

a. The curved surface area :Cs = ∏ r l = 3.14 x 5 cm x 13 cm = 204.1 cm2

So, the curved surface area of cone is 204.1 cm 2

b. The base area : Ba = ∏r 2

= 3.14 x 5 cm x 5 cm = 78.5 cm 2 So, the base area of cone is 78.5 cm 2

c. the surface area = ?

the surface area = Cs + Ba = 204.1 cm2 + 78.5 cm2 = 285.6 cm2

so, the surface area of cone is 285.6 cm2

d. volume = Ba . h

= 78.5 cm2 x 12 cm

= 314 cm3

So, the volume of cone is 314 cm3

EXERCISE

Given that the curved surface of cone beside is 550 cm2 and the radius is 7 cm

Find : a.The slant heightb.The surface area of the

conec.The height of cone

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Deti Nur KarinaFiona SalfadillaRifda Nadifah

Umroh Indah Lestari

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