For the amusement of the guests, some hotels have elevators on the outside of the building. One such hotel is 400 feet high. You are standing by a window 100 feet above the ground and 150 feet away from the hotel, and the elevator descends at a constant speed of 20 ft/sec, starting at time t = 0, where t is time in seconds. Let θ be the angle between the line of your horizon and your line of sight to the elevator. 4 (a) Find a formula for h(t), the elevator's height above the ground as it descends from the top of the hotel. h(t) = (b) Using your answer to part (a), express θ as a function of time t. θ(t) = Find the rate of change of θ with respect to t. dθ dt = (c) The rate of change of θ is a measure of how fast the elevator appears to you to be moving. At what time does the elevator appear to be moving fastest? time = seconds At what height does the elevator appear to be moving fastest?

Answers

Answer 1

9514 1404 393

Answer:

  a.  h(t) = -20t +400

  b.  θ(t) = arctan(2 -2/15t); dθ/dt = -30/(1125 -120t +4t^2)

  c.  15 seconds; 100 ft

Step-by-step explanation:

a. The initial height of the elevator is 400 ft. The rate of change of height is -20 ft/s, so the height equation can be ...

  h(t) = -20t +400

__

b. The tangent of the angle above the line of sight is "opposite"/"adjacent":

  tan(θ) = (h(t) -100)/(150) = -2/15t +2

  θ(t) = arctan(2 -2/15t) . . . . radians

The derivative of the angle function is ...

  dθ/dt = 1/(1+(2 -2/15t)^2)(-2/15)

  dθ/dt = -30/(1125 -120t +4t^2)

__

c. The value of dθ/dt will have a peak where the denominator has a minimum, at t = -(-120)/2(4)) = 15. (The quadratic vertex coordinate is t=-b/(2a).)

The elevator appears to be moving fastest at t=15 seconds.

The height at that time is ...

  h(15) = 400 -20(15) = 100

The elevator appears to be moving fastest when it is at eye level, 100 ft above the ground.


Related Questions

A person working with his cousin can refinish a table in 3 hours. Working alone, his cousin can complete the job in 12 hoursHow long would it take the person to refinish the table working alone?

Answers

Answer:

It is either 4 or 9.

Step-by-step explanation:

because you have to subtract or divide

through: (1, 3) and (-3,-5)

Answers

☆Answer : (X1, Y1) = (1, 3) (X2, Y2) = (-3, -5)

m = (Y2 - Y1)/(X2 - X1)

m = (-5 - 3)/(-3 - 1)

m = -8/-4

m = 2

I need to answer the bottom question please help me ASAP

Answers

Answer:

60 degrees

Step-by-step explanation:

Because line ED exists, the sum of 100, 20, and x must be 180. So, just solve for x in the equation 100 + 20 + x = 180

20 + x = 80

x = 60

Precalc!! Please help

Answers

Answer:

Step-by-step explanation:

1

19. Round the number 347 500 to the nearest 1000; 10 000 and 100 000.
To the nearest 1000
To the nearest 10 000
To the nearest 100 000

Answers

Answer:

34800, 350000, 300000

Step-by-step explanation:

5>=5

34800

7>=5

350000

4<=5

300000

100.00 decreased by 20%
Please help

Answers

Answer: If Percentage decrease % = 20%, (1 - Percentage decrease %) = 1 - 20% = 100/100 - 20/100 = 80/100 = 0.8 => Percentage decreased number = 0.8 × Initial value

Step-by-step explanation: Number 100 decreased by 20% (20 percent) of its value (percentage decrease) and calculated absolute change (actual difference)

In the equation y ≈7x-9,if x≥2, then what is the value of y?​

Answers

Answer:

y[tex]\geq[/tex]5

Step-by-step explanation:

7(2)-9

14-9

5

y[tex]\geq[/tex]5

Rewrite the expression with
parentheses to equal the
given value.
3x 8-5 + 3

value: 12

Answers

3 x (8 - 5) + 3

Parentheses go first here, so 8 - 5 is 3.
Multiplication goes next, so 3 x 3 is 9.
Addition goes last, so 9 + 3 is 12.

Given: DE is a midsegment of ∆C. Show all work. Find the value of x and y. What is the length of C?

Answers

Answer:

Find out the value of x.

To prove

Definition of mid- segment

It is a segment connecting the midpoints of two sides of a triangle.

It is always parallel to the third side, and the length of the midsegment is half the length of the third side.

As shown in the triangle given below.

As given

DE = 5x and BC = 11x – 15

Thus

15 = 11x - 10x

15 = x

Therefore the value of x is 15 .

Step-by-step explanation:

Which value for x satisfies the equation 3x−6=15?

Answers

Answer:

x= 7

Step-by-step explanation:

1. Add 6 to both sides

2. simplify

3. Divide by the same term

4. simplify

Answer:

7

Step-by-step explanation:

3x7=21

= 21 - 6 = 15

I hope you find it helpful ..

Good luck

Sally Jones had a policy with a $250 deductible which paid 80% of her covered charges less deductible. She had medical expenses of $18,240.00. What is S

Answers

Answer

Find out the  insurance company's payment .

To proof

Deductible

The deductible is the amount of money you will pay in an insurance claim before the company starts paying you insurance coverage .

As given

Sally Jones had a policy with a $250 deductible which paid 80% of her .covered charges less deductible

She had medical expenses of $18,240.00.

Amount becomes after deducting deductible = $18,240 -  $250

                                                                                   = $17990

80 % is written in the decimal form

now 80% of the Amount after deducting deductible

= $ 14392

Therefore $ 14392 is the insurance company's payment .

 Remember To Stay In School

Wink Wink

Answer:3,848

Step-by-step explanation:I took the test.

ple help me quick thank you:)​

Answers

Answer:

z> 5/4

To graph, use the open dotted line and put it at point 5/4 aka 1.25 going towards the right because it is greater than.

Step-by-step explanation:

Isolate your variable (z) by multiplying both sides of the equation by 5/3.

z> 5/4


The perimeter of the triangle is
equal to the area of the rectangle.
What is the value of x?

Answers

Answer:

x=-21

Step-by-step explanation:

make the equation

2x+9x-1+40=6(x-11)

simplify

11x+39=6x-66

solve

5x=-105

x=-21


Solve for x and y !!!!!!!!!!!

Answers

Answer:

x=12; y=138.

Step-by-step explanation:

1. 4x+(3x+6)=90 - to calculate 'x';

3x+6+y=180 - then to calculate 'y';

2. 7x+6=90; ⇒ x=12;

3. 3*12+6+y=180; ⇒ y=138°.

I 13.12.21 Mather asianmen I choose the best answert the next two numbers in the pattern 1, 4, 9, 16 are. (A) 26,36 (B) 25, 36 (C) 24,35 (D) 36,48​

Answers

Answer:

(B) 25, 36

Step-by-step explanation:

1 = 1²

4 = 2²

9 = 3²

16 = 4²

25 = 5²

35 = 6²

Use a system of equations to find the partial fraction decomposition of the rational expression. Solve the system using matrices.
[tex] \frac{3x ^{2} + 3x - 2 }{(x + 1)^{2} (x - 1)} = \frac{a}{x + 1} + \frac{b}{x - 1} + \frac{c}{(x + 1)^{2} } [/tex]
A=
B=
C=​

Answers

Combine the fractions on the left with a common denominator:

[tex]\dfrac a{x+1} + \dfrac b{x-1} + \dfrac c{(x+1)^2} = \dfrac{a(x+1)(x-1) + b(x+1)^2 + c(x-1)}{(x-1)(x+1)^2}[/tex]

It follows that

[tex]3x^2+3x-2 = a(x+1)(x-1) + b(x+1)^2 + c(x-1)[/tex]

Expand the right side and collect like powers of x :

[tex]3x^2+3x-2 = a(x^2-1) + b(x^2+2x+1) + c(x-1)[/tex]

[tex]3x^2+3x-2 = (a+b)x^2 + (2b + c)x -a +b - c[/tex]

Then we have the system of equations

[tex]\begin{cases}a+b=3\\2b+c=3\\-a+b-c=-2\end{cases}[/tex]

or in matrix form,

[tex]\begin{bmatrix}1&1&0\\0&2&1\\-1&1&-1\end{bmatrix} \begin{bmatrix}a\\b\\c\end{bmatrix} = \begin{bmatrix}3\\3\\-2\end{bmatrix}[/tex]

Compute the determinant of the coefficient matrix:

[tex]\det\begin{bmatrix}1&1&0\\0&2&1\\-1&1&-1\end{bmatrix} = -4[/tex]

Then the inverse of the coefficient matrix is equal 1/det times the adjugate of the coefficient matrix (a.k.a the transpose of the cofactor matrix):

[tex]\begin{bmatrix}1&1&0\\0&2&1\\-1&1&-1\end{bmatrix}^{-1} = \dfrac1{-4} \begin{bmatrix}-3 & -1 & 2 \\ 1 & -1 & -2 \\ 1 & -1 & 2\end{bmatrix}^\top = -\dfrac14 \begin{bmatrix}3&-1&-1\\1&1&1\\-2&2&-2\end{bmatrix}[/tex]

Multiply both sides of the equation by the inverse :

[tex]\begin{bmatrix}a\\b\\c\end{bmatrix} = -\dfrac14 \begin{bmatrix}3&-1&-1\\1&1&1\\-2&2&-2\end{bmatrix} \begin{bmatrix}3\\3\\-2\end{bmatrix} = \begin{bmatrix}2\\1\\1\end{bmatrix}[/tex]

So, we have a = 2 and b = c = 1, and the partial fraction decomposition is

[tex]\dfrac{3x^2+3x-2}{(x+1)^2(x-1)} = \dfrac 2{x+1} + \dfrac 1{x-1} + \dfrac 1{(x+1)^2}[/tex]

Answer:

A = 2B = 1C = 1

Step-by-step explanation:

One can solve for a, b, c a little more directly than using a system of 3 equations.

If we multiply the rational expression by (x+1)², we get ...

  (3x² +3x -2)/(x -1) = (x+1)²(a/(x+1) +b/(x-1)) +c

Evaluating this for x = -1 gives ...

  (3(-1)² +3(-1) -2)/(-1 -1) = c

  -2/-2 = 1 = c

Similarly, multiplying by (x -1) gives ...

  (3x² +3x -2)/(x +1)² = (x -1)(a/(x +1) +c/(x +1)²) + b

Evaluating this for x = 1 gives ...

  (3·1² +3·1 -2)/(1 +1)² = b

  4/4 = 1 = b

Now, we need to find the value of 'a'. The identity will hold true for any value of x, so we can see what happens when we substitute x=0. We can use the values of 'b' and 'c' that we found above.

  (3·0² +3·0 -2)/((0 +1)²(0 -1)) = a/(0 +1) +1/(0 -1) +1/(0 +1)²

  -2/-1 = a -1 +1   ⇒   a = 2

_____

System of equations solution

When the terms of the right-side expansion are combined, the numerator of the result is ...

  a(x +1)(x -1) +b(x +1)^2 +c(x -1) = (a+b)x² +(2b+c)x +(-a+b-c) ≡ 3x² +3x -2

Equating the coefficients gives the system of equations whose augmented matrix is:

  [tex]\left[\begin{array}{ccc|c}1&1&0&3\\0&2&1&3\\-1&1&-1&-2\end{array}\right][/tex]

Transforming this to reduced row-echelon form using any of a variety of available tools gives ...

  [tex]\left[\begin{array}{ccc|c}1&0&0&2\\0&1&0&1\\0&0&1&1\end{array}\right][/tex]

which tells you the solution is (A, B, C) = (2, 1, 1).

Find the equation of the line.

Answers

Answer:

y= 4/1x +1

Step-by-step explanation:

the number on the y axis is the b and you do rise over run to find m you rise (so you go up or down) 4 times and run( go to the sides) once.

rise 4

-------- = -----

run 1

Answer:

y = 3x + 1

Step-by-step explanation:

Slope: As it rises 3, it runs 1

Slope = Change in y/change in x

Slope = 3/1

y - intercept = 1 ,the point of intersection

Equation : y = mx + b

m = slope

b = y-intercept

Equation : y = 3x + 1

-Chetan K

Four times the product of a number x and a number y is equal to 20.

Answers

Step-by-step explanation:

4x×y=20

.....

..................................

The expression for four times the product of a number x and a number y is equal to 20 is 4xy = 20.

Given,

Four times the product of a number x and a number y is equal to 20.

We need to write the expression.

What is the meaning of the mathematical terms?

- 2 times M = 2 x M

- Product of M and N = M x N

- 3 more than M = M + 3

- 3 less than M = M - 3

Find the expression.

We have,

Four times the product of a number x and a number y is equal to 20.

Here,

The product of a number x and a number y can be written as:

= (x) x y

Four times the product of a number x and a number y can be written as:

= 4 x [ (x) x y ]

- is equal to 20 can be written as:

= 20

Now,

We get,

4xy = 20

Thus the expression for Four times the product of a number x and a number y is equal to 20 is 4xy = 20.

Learn more about how to write an expression here:

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Two points are shown on the number line. Which value is best represented by the point F? 

Answers

Answer:

I believe its d

which matrix multiplication is defined?​

Answers

D is a matrix multiplication that is defined

which is the graph of y -3 equals -2/3 (x + 6)
NO LINKS​

Answers

Step-by-step explanation:

This is point-slope form:

[tex]y-y1=m(x-x1)[/tex]

in this case:

[tex]y-3=-\frac{2}{3} (x+6)[/tex]

Looking at the structure of point slope form up top, you can find the slope and one point.

[tex]m=-\frac{2}{3} \\x1=-6\\y1=3\\(-6,3)[/tex]

Now, just find the graph with a slope of [tex]-\frac{2}{3}[/tex] that passes through (-6, 3). It's hard to see on the image, but that looks like the top left.

By the way, what's the "no links" thing about? I just came back to this site after a year away

a scale diagram, 0.125 inch represe
5 feet. How many inches represent
pot?
0.001
0.01
0.1
0.12
Math

Answers

Answer:

the scale diagram is 9.12

what's 2x+3y=1,470 in slope intercept form?​

Answers

Slope intercept form: y = mx + b
You need to separate x and y
2x + 3y = 1,470
Subtract 2x from both sides
3y = -2x + 1470
Divide by 3

Solution: y = -2/3x + 490

Yes, but on this site, how can I make sure that this answer is correct or wrong, please, I don't know?

Answers

I think you forgot to add a bit of information
If you are referring to Brainly, there is not a completely effective way to do this, however members often rate each other’s answers. If an answer has multiple five stars, or was solved by someone with a credible ranking, it is more likely to be correct.

Find the simplified product. 5/n+1 times n+1/n+3

Answers

[tex]\left(\dfrac{5}{n+1}\right) \left( \dfrac{n+1}{n+3} \right)\\\\\\=\dfrac{5(n+1)}{(n+1)(n+3)} \\\\\\=\dfrac{5}{n+3}[/tex]

Haala buys 13 identical shirts and 22 identical ties for £363.01 the cost of the shirt is £15.35 find the cost of the tie

Answers

Using linear system of equations, the cost tie is £7.43.

Linear equations -

In everyday life, we can utilize linear equations to compare prices, make predictions, create budgets, and more. When all of the variables have a highest power of one, an equation is considered to be linear. Each variable is reliant on the others. A one-degree equation is another name for this kind of equation. Continue reading to learn how to solve a linear equation in one or two variables using its standard form, formula, graph, and rules.

Given,

Haala buys 13 identical shirts and 22 identical ties for £363.01 the cost of the shirt is £15.35,

According to question,

let cost of shirt = x

cost of tie = y

Now putting it in the equation,

13x + 22y = 363.01

given x = 15.35

⇒ y = 363.01 - 13(15.35) / 22

y = 363.01 - 199.55 / 22

y = 7.43

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If 12 cats can kill 12 mice in 12 hours, how many hours will it take for 2021 cats to kill 2021 mice

Answers

Step-by-step explanation:

168 hours I guess

have a food day

an investment had return of 13% if inflation was 4.1% what was your real return ?

Answers

Answer: 8.9%

Step-by-step explanation: 13 - 4.1

Janine is 25 and has a good job at a biotechnology company. Janine estimates that she will need $875,000 in her total retirement nest egg by the time she is 65 in order to have retirement income of $20,000 a year. (She expects that Social Security will pay her an additional $15,000 a year.) She currently has $5,000 in an IRA, an important part of her retirement nest egg. She believes her IRA will grow at an annual rate of 8 percent, and she plans to leave it untouched until she retires at age 65. How much money will Janine have to accumulate in her company’s 401(k) plan over the next 40 years in order to reach her retirement income goal? Use Exhibit 1-A.

Answers

We have that for the Question, it can be said that

The amount of money Janine will have to accumulate in her company’s 401(k) plan over the next 40 years is

$ 766377.4

From the question we are told

Janine is 25 and has a good job at a biotechnology company.

Janine estimates that she will need $875,000 in her total retirement nest egg by the time she is 65 in order to have retirement income of $20,000 a year. (She expects that Social Security will pay her an additional $15,000 a year.) She currently has $5,000 in an IRA, an important part of her retirement nest egg. She believes her IRA will grow at an annual rate of 8 percent, and she plans to leave it untouched until she retires at age 65. How much money will Janine have to accumulate in her company’s 401(k) plan over the next 40 years in order to reach her retirement income goal? Use Exhibit 1-A.

IRA Sum = $ 5000 Growth ratio of IRA= 8%Growth period = 40 years

Generally the equation for the IRA Amount  at Retirement  is mathematically given as

IAR= 5000 * 1.08^(40)

=  108622.6

Since estimate is at

$875,000  

Therefore

Accumulation in 401,000 = 875000 - 108622.6

Accumulation in 401,000 = 766377.4

Hence

The amount of money  Janine will have to accumulate in her company’s 401(k) plan over the next 40 years is

$ 766377.4

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Plz solve. The question is in the picture. 100 points and brainliest.

Answers

Answer:

A

Step-by-step explanation:

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