This document defines and explains the key elements of a cone. It defines a cone as a three-dimensional shape that tapers from a circular base to a single point called the apex or vertex. The key elements are the base, curved surface, height, slant height, and radius. It provides formulas to calculate the surface area of a cone using the radius and slant height. An example problem demonstrates how to use the given information to calculate the slant height, surface area, and height of a cone. Exercises at the end provide additional practice calculating values for cones.

1. BUGENVIL 
Presentated by
Annisa Khairati Salam
Annisa Roudlotul Jannah
Antania Nur’ Avyanti
Hazna Putri Salsabilla
Lina Nuruzzati
Wike Maylani

2. CONE
a.) Definition of Cone
 A cone is a dimensional geometric shape that
tapers smoothly from a base (usually flat and
circular) to a point called the apex or vertex.
h : height
s : slant height
r : radius

3. B. ELEMENTS OF A CONE
a) A cone has 2 planes, namely the base and the
right planes. The base is circular plane of radius r
or BO, while the right plane is a curved which is
also called curved surface.

4. b) A cone has an edge, that is the base edge
which is in the form of a circle.
Circle

5. c) The line segment joining point O to A is called the
height of the cone. Usually it is notated by h or t.
d) The line segment of the curved surface joining vertex
A and the points of the circle are called slant heights.
A slant height is usually notated by s or l.

6. C. PaRt of Cone
 The circle at the bottom of a cone defines the
shape of the cone, so all of the parts of a circle
are important parts of a cone. For example,
the radius is an integral part of finding the
volume of a cone.

8. D. THE SURFACE AREA OF A CONE
Sector TAA’ is in the circle of radius TA or of
radius s/l, so that :
The area of sector TAA’ = the length of arc AA’
The circle area the circle circumference
The area of sector TAA’ = 2πr
πs 2 2πs
The area of sector TAA’ = 2πr × πs 2
2πs
The area of sector TAA’ = πrs
The area of the curved surface = the area of
sector TAA’ = πrs

9. The surface area of a cone is equal to the
area of its net, or it can be expressed by the
following formula.
L = area of curved surface + circle area
= π rs + π r2
= π r (s + r)

10. The formula of the surface area of a cone is:
L = π r (s + r)
Where L = the surface area of the cone
π = 22 or π = 3,14
7
r = circle radius (base plane of the cone)
s = slant height of the cone

11. E.) EXAMPLE
1) A cone has a base radius of 7 cm. If the area of
its curved surface is 550 cm2 and π = 22 find :
7
a. The slant height
b. The surface area of the cone
c. The height of the cone

12. Solution:
Given that r = 7 cm, area of curved surface = 550 cm2,
and π = 22
7
a. The area of curved surfaces = π rs
550 = 22 × 7 × s
7
550 = 22s
s = 550
22
s = 25 cm

13. b. L = π r (s + r)
= 22 × 7 × (25 + 7)
7
= 22 × 32
= 704 cm2
c.
⇔ t = 24 cm.

14. F.) EXERCISE
1) A cone has a base radius of 14 cm. If the area of
its curved surface is 957 cm2 and π = 22 find
7
a. The slant height
b. The surface area of the cone

15. Solution:
Given that r = 7 cm, area of curved surface =
957 cm2, and π = 22
7
a. The area of curved surfaces = πrs
957 = 22 × 7 × s
7
957 = 22s
s = 957
22
s = 29 cm

16. b. L = π r (s + r)
= 22 × 7 × (29 + 7)
7
= 22 × 36
= 792 cm2

17. QUOTES
If A is a 'success', then the formula is 'A = X + Y
+ Z', where X is the 'working', Y is 'play', and Z
is keep your mouth to keep it closed.
Jika A adalah ‘sukses’, maka rumusnya adalah
‘A=X+Y+Z’, dimana X adalah ‘kerja’, Y adalah
‘bermain’, dan Z adalah jaga mulut anda agar
tetap tertutup.
Pendidikan adalah mata uang yang berlaku di
seluruh dunia

18. VISIT :
http://www.deepyudha.blogspot.com/
Our beloved teacher Lilis Yuningsih,
S.Pd,MM

19. THANKS FOR
YOUR
ATTENTION 