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kirill115 [55]
3 years ago
11

The surface area, S, of a sphere of radius r feet is S = S(r) = 4πr^2. Find the instantaneous rate of change of the surface area

with respect to the radius r at r = 8.
Mathematics
1 answer:
vesna_86 [32]3 years ago
4 0
This is the derivative of S with respect to r, evaluated at r=8.
dS/dr = 8πr
Substituting r=8 into the above gives the answer of 64π.
You might be interested in
The ratio of the loudness of lala's earphones to the loudness of polina's earphones to the loudness of goffy's earphones is 6:5:
tresset_1 [31]
Let:
Lala be l
Polina be P
Goffy be G
the respective ratio is 6:5:3
Given that Polina's loudness is 420 decibels then the total loudness will be calculated as follows:
Total ratio=6+5+3=14
hence total loudness will be:
14/5×420
=1,176 decibels 
3 0
3 years ago
A. Write the equation of the line that represents the linear approximation to the following function at the given point a.
anastassius [24]

Answer:

a) f(x) = 4 - x²

The linear approximation of the function at a=1 is

L(x) = 5 - 2x at a = 1

b) The graph of the function and the linear approximation at that point is attached to this solution.

The curve represent the real function,

f(x) = 4 - x²

The straight line represents the linear approximation of the function at a=1.

L(x) = 5 - 2x

The curve and the function evidently cross paths at x=1 and understandably so.

c) Using the linear approximation obtained at a = 1.

f(1.1) = 2.8

Using the actual function, the actual value of f(1.1) = 2.79

d) Percent error = 0.358%

Step-by-step explanation:

f(x) = 4 - x²

a) The linear approximation of the function at the given point is given as

L(x) = f(a) + f'(a) [x - a]

f(x) = 4 - x²

a = 1

f(a) = 4 - 1² = 3

f'(x) = -2x

f'(a) = -2(1) = -2

L(x) = f(a) + f'(a) [x - a]

L(x) = 3 + (-2)(x - 1)

L(x) = 3 -2x + 2

L(x) = 5 - 2x

L(x) = -2x + 5

f(x) = 4 - x²

L(x) = 5 - 2x at a = 1

b) The graph of the function and the linear approximation at that point is attached to this solution.

The curve represent the real function,

f(x) = 4 - x²

The straight line represents the linear approximation of the function at a=1.

L(x) = 5 - 2x

The curve and the function evidently cross paths at x=1 and understandably so.

c) Use the linear approx. to estimate the given fxn value.

f(1.1)

L(x) = 5 - 2x

L(1.1) = 5 - 2(1.1) = 2.8

Using the function, the actual value of f(1.1) = 4 - 1.1² = 2.79

d) Compute the percent error in your approximation, 100*Iapprox-exactI/IexactI, where the exact value is given by a calculator

Percent error

= 100% × (|approx - exact|)/exact

Approximated value = 2.8

Exact value = 2.79

Percent error = 100% × (2.8-2.79)/2.79

Percent error = 0.358%

Hope this Helps!!!

6 0
4 years ago
The height h in feet of a ball after t seconds is given h=176t-16t^2. how long did it take for the ball to hit the ground?
Molodets [167]
Here's our equation.

h=176-16t^2

Let's reorder this so t² comes before t.

h=-16t^2+176t

We want to find out when the ball hits the ground. Essentially, <em>what is t when h=0?</em>
Let's plug in 0 for h and solve.

0=-16t^2+176t

From here we can use a number of methods to solve.
Methods such as splitting the middle, quadratic formula, etc. are not necessary for this equation, however. The best method here is just plain factoring.

-16t² and 176t are both divisible by 16t.

0=16t(-t+11)

Now we want t to equal zero. If either of those factors were zero, then the whole thing would be zero when we multiply by it. The first option is obvious. If t were 0, 16t would be 0. That's when the ball is first kicked off the ground. The other, 11-t, works out to be t = 11.
6 0
3 years ago
A man starts at a point A and walks 18 feet north. He then turns and walks due east at 18 feet per second. If a searchlight plac
34kurt

Answer:

1/10 per sec

Step-by-step explanation:

When he's walked x feet in the eastward direction, the angle Θ that the search light makes has tangent

tanΘ = x/18

Taking the derivative with respect to time

sec²Θ dΘ/dt = 1/18 dx/dt.

He's walking at a rate of 18 ft/sec, so dx/dt = 18.

After 3seconds,

Speed = distance/time

18ft/sec =distance/3secs

x = 18 ft/sec (3 sec)

= 54ft. At this moment

tanΘ = 54/18

= 3

sec²Θ = 1 + tan²Θ

1 + 3² = 1+9

= 10

So at this moment

10 dΘ/dt = (1/18ft) 18 ft/sec = 1

10dΘ/dt = 1

dΘ/dt = 1/10 per sec

8 0
3 years ago
I need help with 6 &amp; 8
zimovet [89]
1. We need to get rid of those pesky parentheses. We do this by distributing the 3.

2. We need to get "n" by itself, so we add 9 to both sides.

3. Add like terms.

4. Now, we need to get rid of the -9, so we divide both sides by -9. Remember that dividing by negative numbers changes the direction of the "greater than or equal to" symbol.

5. We divide, and the negatives cancel.

I wrote the answer both ways so that I could tell what the number line needed to look like.

7 0
3 years ago
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