Exercise 14 Page 852

The surface area of a sphere is four times the product of π and the square of the radius.

12.6cm^2

Practice makes perfect

The surface area of a sphere is four times the product of π and the square of the radius. S=4π r^2We are told that the circumference is 2π cm. Let's use the formula for the circumference C of a circle to find the radius r.

C=2π r

Substitute

C= 2π

2π=2π r

DivEqn

.LHS /2π.=.RHS /2π.

1=r

RearrangeEqn

Rearrange equation

r=1

Let's now substitute 1 for r in the formula for the surface area and simplify the right-hand side.

S=4π r^2

Substitute

r= 1

S=4π ( 1)^2

▼

Simplify right-hand side

CalcPow

Calculate power

S=4π (1)

IdPropMult

Identity Property of Multiplication

S=4π

UseCalc

Use a calculator

S=12.56...

RoundDec

Round to 1 decimal place(s)

S≈ 12.6

The surface area of the given sphere to the nearest tenth is 12.6cm^2.

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Exercises p.852-855

Exercise 14 Page 852

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