Page 52 - Math Course 3 (Book 2)

Geometric Surface Area: Cones
Mo. 8

Lesson 3

oblique cone
KEY CONCEPTS:
A cone where the axis is not the altitude.
1. Find lateral areas of cones.
2. Find surface areas of cones.

axis altitude
MO. 8 - L3a

Lateral and Surface Areas of X
Cones

Key Concept

Vocabulary A-Z
Let us learn some vocabulary Lateral Area of a Cone

circular cones If a right circular cone has a lateral
Circular Cones have the following characteristics. area of L square units, a slant
height of units, and the radius
• The base is a circle and the vertex is the point V. of the base is r units, then

• The axis is the segment with endpoints that are L = πr .
the vertex and the center of the base. r

Vertex

Surface Area of a Cone
Axis of
symmetry H
If a right circular cone has a r
Base R surface area of T square units
a slant height of units, and the
radius of the base is r units, then
right cone T = πr + πr²
A cone with an axis that is also the altitude is
called a right cone.

Axis of is also
an altitude. h slant height

r

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