1. Find the surface area of the cone.

Round to the nearest tenth.

2. Find the surface area of a cone

with a radius of 6 feet and a

slant height of 10 feet. Round to

the nearest tenth.

3. Find the slant height of a cone with a radius of 4 centimeters and a surface area of 48 square centimeters.

• great circle

• hemisphere

• Recognize and define basic properties of spheres.

• Find surface areas of spheres.

Spheres and Circles

In the figure, O is the center of the sphere, and plane P intersects the sphere in circle R. If OR = 6 centimeters and OS = 14 centimeters, find RS.

Spheres and Circles

Answer: RS is approximately 12.6 centimeters.

The radius of circle R is segment and S is a point on circle R and on sphere O. Use the Pythagorean Theorem for right triangle ORS to solve for RS.

Simplify.

Pythagorean Theorem

Subtract 36 from each side.

Use a calculator.

A. A

B. B

C. C

D. D

A. 7.4 in.

B. 8.5 in.

C. 11 in.

D. 8.7 in.

In the figure, O is the center of the sphere, and plane U intersects the sphere in circle L. If OL = 3 inches and LM = 8 inches, find OM to the nearest tenth.

http://www.ca.geometryonline.com/

Surface Area

A. Find the surface area of the sphere, given a great circle with an area of approximately 907.9 square centimeters.

The surface area of a sphere is four times the area of the great circle.

Answer: The surface area is approximately 3631.6 square centimeters.

Surface area of a sphere

Multiply.

Surface Area

B. Find the surface area of a hemisphere with a radius of 3.8 inches.

A hemisphere is half of a sphere. To find the surface area, find half of the surface area of the sphere and add the area of the great circle.

Answer: The surface area is approximately 136.1 square inches.

Surface area of a hemisphere

Use a calculator.

Substitution

1. A

2. B

3. C

4. D

A. 183.2 cm2

B. 366.4 cm2

C. 287.8 cm2

D. 1151.1 cm2

A. Find the approximate surface area of the sphere, given a great circle with an area of approximately 91.6 square centimeters.

1. A

2. B

3. C

4. D

A. 128.7 in2

B. 257.4 in2

C. 386.0 in2

D. 514.7 in2

B. Find the approximate surface area of a hemisphere with a radius of 6.4 inches.

Find the surface area of a ball with a circumference of 24 inches to determine approximately how much leather is needed to make the ball.

Circumference of a circle

First, find the radius of the sphere.

C = 24

Use a calculator.

Divide each side by

Answer: The surface area is approximately 183.3 square inches.

Next, find the surface area of the sphere. Be sure to round to the nearest tenth.

Surface area of a sphere

Use a calculator.

1. A

2. B

3. C

4. D

A. 51.6 in2

B. 254.5 in2

C. 412.5 in2

D. 103.1 in2

Find the surface area of a ball with a circumference of 18 inches to determine how much leather is needed to make the ball.