Lesson 11-5 Pages 578-582 Surface Area: Pyramids and Cones

Lesson 11-5 Pages 578-582

Surface Area: Pyramids and Cones

What you will learn!

1. How to find surface area of pyramids.

2. How to find surface area of cones.

Lateral faceLateral faceSlant heightSlant heightLateral areaLateral area

What you really need to know!

The sides of a pyramid are called lateral faces.

What you really need to know!The sides are triangles. The height of each lateral face is called the slant height.

What you really need to know!The sum of the areas of the lateral faces is called the lateral area of a pyramid.

What you really need to know!The surface area of a pyramid is the lateral area plus the area of the base.

What you really need to know!The surface area of square pyramid is made up of 4 triangles and a square.

What you really need to know!The surface area S of a cone with slant height l and radius r is the lateral area plus the area of the base.

What you really need to know!

S = rl + r2

The lateral area of a cone with slant height l is one-half the circumference of the base, 2r, times l.

Link to Pre-Made Lesson

Example 1:

88)9.882

1(4

Find the surface area of the square pyramid:

24.206 ft

Example 2:

A canopy is in the shape of a square pyramid that is 3.4 meters on each side. The slant height is 2 meters. How much canvas is used for the canopy?

)24.32

1(4

26.13 m

Canvas is not needed for the square base. We only need to find the lateral area.

Example 3:

Find the surface area of the cone. Round to the nearest tenth.

2rrl 25.3105.3

24.148 ft

Page 580

Guided Practice

#’s 4-7

Pages 578-580 with someone at home and

study examples!

Read:

Homework: Pages 580-582

#’s 8-13, 17-21, 24-31, 34-39

Page

751

Lesson 11-5