Given the curve [tex]\displaystyle \large{y=e^{-x}\sin x \ \ (x\geq 0)[/tex] let the area enclosed by the curve and the x-axis (above the x-axis) be S0, S1, S2, ... , Sn, ... in order from y-axis. Find [tex]\displaystyle \large{ \lim_{n \to \infty} \sum_{k=0}^{n} S_k}[/tex]

Answers

Answer 1

The given curve crosses the x-axis whenever x is a multiple of π, and it lies above the x-axis between consecutive even and odd multiples of π. So the regions with area S₀, S₁, S₂, ... are the sets

[tex]R_0 = \left\{(x, y) : 0 \le x \le \pi \text{ and } 0 \le y \le e^{-x}\sin(x)\right\}[/tex]

[tex]R_1 = \left\{(x, y) : 2\pi \le x \le 3\pi \text{ and } 0 \le y \le e^{-x}\sin(x)\right\}[/tex]

[tex]R_2 = \left\{(x, y) : 4\pi \le x \le 5\pi \text{ and } 0 \le y \le e^{-x}\sin(x)\right\}[/tex]

and so on, with

[tex]R_k = \left\{(x, y) : 2k\pi \le x \le (2k+1)\pi \text{ and } 0 \le y \le e^{-x}\sin(x)\right\}[/tex]

for natural number k.

The areas themselves are then given by the integral

[tex]S_k = \displaystyle \int_{2k\pi}^{(2k+1)\pi} \int_0^{e^{-x}\sin(x)} dy \, dx = \int_{2k\pi}^{(2k+1)\pi} e^{-x}\sin(x) \, dx[/tex]

Integrate by parts twice. Take

[tex]u = e^{-x} \implies du = -e^{-x} \, dx[/tex]

[tex]dv = \sin(x) \, dx \implies v = -\cos(x)[/tex]

so that

[tex]\displaystyle \int e^{-x}\sin(x) \, dx = -e^{-x}\cos(x) - \int e^{-x}\cos(x) \, dx[/tex]

then

[tex]u = e^{-x} \implies du = -e^{-x} \, dx[/tex]

[tex]dv = \cos(x) \, dx \implies v = \sin(x)[/tex]

so that

[tex]\displaystyle \int e^{-x}\cos(x) \, dx = e^{-x}\sin(x) + \int e^{-x}\sin(x) \, dx[/tex]

Overall, we find

[tex]\displaystyle \int e^{-x}\sin(x) \, dx = -e^{-x}\cos(x) - e^{-x}\sin(x) - \int e^{-x}\sin(x) \, dx[/tex]

or

[tex]\displaystyle \int e^{-x}\sin(x) \, dx = -\frac12 e^{-x} (\cos(x)+\sin(x)) + C[/tex]

Using the antiderivative and the fundamental theorem of calculus, we compute the k-th area to be

[tex]\displaystyle S_k = -\frac12 e^{-(2k+1)\pi} (\cos((2k+1)\pi)+\sin((2k+1)\pi)) + \frac12 e^{-2k\pi} (\cos(2k\pi)+\sin(2k\pi))[/tex]

[tex]\displaystyle S_k = \frac12 e^{-2k\pi} \cos(2k\pi) \left(e^{-\pi} + 1\right)[/tex]

[tex]\displaystyle S_k = \frac{e^{-\pi}+1}2 e^{-2k\pi}[/tex]

Since [tex]\left|e^{-2\pi}\right|<1[/tex], the sum we want is a convergent geometric sum. As n goes to ∞, we have

[tex]\displaystyle \lim_{n\to\infty} \sum_{k=0}^n S_k = \frac{e^{-\pi}+1}2 \cdot \frac1{1 - e^{-2\pi}} = \boxed{\frac{e^\pi+1}{4\sinh(\pi)}}[/tex]


Related Questions

Calculate the frequency of a wave with a speed of 130 m/s and a wavelength of 2.5

Answers

Answer:

  52 Hz

Step-by-step explanation:

We can divide the speed by the wavelength to find the number of waves propagated in one second:

  (130 m/s)/(2.5 m/wave) = 52 waves/s

The SI unit of frequency is the Hertz, equal to one cycle per second.

The frequency of this wave is 52 Hz.

_____

Additional comment

The use of the unit Hz to signify frequency was adopted in 1933, but did not replace the unit "cycles per second" (CPS) until a number of years later.

my Christmas present to you​

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Answer:

super man

Step-by-step explanation:

if ur good at math, pls help. will get brainliest

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Answer: y = -x - 3

Using the parent function/formula y = mx +b, you can use the slope formula [tex]\frac{x_{2}-x_1 }{y_2-y_1}[/tex] to determine that the slope is negative. Then, using the answer to the slope equation (m), you can use 2 points from the table to solve the equation for b. Then just write the equation using y, x, value of m, and value of b.

Tommy bought one dozen donuts. He gave one-sixth of the donuts to his wife. He then gave one-fifth of the remaining donuts to his son. He took the rest to work. How many donuts did Tommy take to work?

Answers

Answer:

8

Step-by-step explanation:

1/6 of 12 is 2

12 - 2 = 10

1/5 of 10 is also 2

10 - 2 = 8

Tommy took 8 donuts to work.

Plot /\ABC: B(-1,-1), and C(4,-1)
——JUST LOOK AT PHOTO AND PLEASE HELP

Answers

Answer:

i dont know sry

Step-by-step explanation:

:)

What inequality is represented by this graph?
O X > 6 O X _< 6 O X<6 OX_>6

Answers

last option in the picture

Problem #3
Imagine you are building a triangular garden. Two sides of the garden measure 230 ft and
360 ft and the included angle between these two sides of the garden measures 38°. What is
the measure of the third side?
С
230ft
38
360ft

Answers

Answer:

b = 115.4 feet

Step-by-step explanation:

b^2 = a^2 + c^2 - 2 (a)(b) x cos B

b^2 = 230^2 + 360^2 - 2(230)(360) x cos(38 degrees)

b^2 = 52,900 + 129,600 - 2(230)(360) x cos(38 degrees)

b^2 = 182,500 - 165,600 x cos(38 degrees)

b = [tex]\sqrt{(16,900)(cos(38)) }[/tex]

b = 115.4 feet

i hope this helps!! :)

Answer:

115.4 ft

Step-by-step explanation:

Solve.

x2=−0.73

What is the solution to the equation?

Enter your answer as a decimal in the box.

x =

Answers

x = -0.365 (If its x(2)=-0.73)

How I solved it:

x^2=-0.73

-0.73÷2=-0.365

//

-0.365×2=-0.73

Therefore, the answer is -0.365.

Answer:

x = -1.46 (if its x/2=-0.73)

x/2=-0.73

-0.73x2=-1.46

therefore,

-1.46/2=-0.73

///

making the answer

-1.46

What function equation is represented by the graph?

Answers

Answer:

f(x) = (2/3)x-2

Step-by-step explanation:

Pick any two points and calculate the slope.  I chose:  (-3,-4) and (3,0).  The Rise/Run, or slope, is (0-(-4))/(3-(-3) or 4/6:  2/3

The y-intercept of the graph is -2 ( the value of y when x=0).

Given y = mx + b

we have

y = (2/3)x - 2

Option 3

Brendan says that the negative of - 1/3
is 3 because they are on ​opposite sides of zero when they are plotted on the number line.

​Is Brendan correct? Explain your answer.

Answers

Answer:

No! Brendan has totally got the wrong idea.

Step-by-step explanation:

Numbers on the right hand side of zero are said to be positive, while, the numbers on the opposite side are said to be negative.

That means Brendan's correct in saying that -1/3 lies on the opposite side of 3, since negative numbers lie on the opposite side of the positives.

But,

Negative "of" a number is the same number with opposite sign.

That is, if a number is 3 units away from the zero, it's negative will also be 3 units away from zero, but on the opposite side.

-1/3 and 3 do not lie at the same distance from zero.

-1/3 would be approached before -1 by walking in the negative direction whereas 3 would be approached after 1.

Therefore, Brendan is wrong as the negative of a number has opposite sign but same "magnitude".

What is the value of the expression Negative 225 divided b (negative 15)?
What is the value of the expression 30 divided by (negative 6)?

Answers

Answer:

-15-5

Step-by-step explanation:

What is the value of the expression Negative 225 divided b (negative 15)?

What is the value of the expression 30 divided by (negative 6)?

I answer for what I understand

-225 : 15 = - 15

30 : (- 6 ) = -5

Given the function f(x) = x2 - x + 7, find each of the following.
f(6)=
f(- 9)=
f(0)

Answers

Answer:

37, 79, 7

Step-by-step explanation:

f(6) = 6² -6 +7

36-6+7 is 37

f(-9) = -9² -9+7

81-9+7 is 79

f(0) = 0² -0+7

0-0+7 is 7

Use long division to find the quotient below. (8x^3-10x^2-19x-15)/(2x-5)

Answers

Answer:

4x2 + 5x + 3

Step-by-step explanation:

please help me with math

Answers

Hi there! :)

5-2b when b=-1; 3.

5-2(-1)

5+2

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5-2(3)

5-6

-1

3(x+8)

3x+24

Hope it helps!

~Answer given by

An Unknown Dreamer

Good luck.

Write the following equation in standard form:`X^{2}+6X=-2`

Answers

Answer:

[tex]x^2 +6x +2=0[/tex]

Step-by-step explanation:

Solve the following system of equations.

2x + y=3
x=2y-1

Make sure there are NO SPACES in your answer. Include a comma in your answer.

ANSWER: {(
)}

Answers

Answer:

x=1,y=1

Step-by-step explanation:

For this problem, we can use the substitution method. Since we know that x is equal to 2y-1, we can rewrite the first equation as 2(2y-1)+y=3. Now solving we get:

4y-2+y=3

5y-2=3

5y=5

y=1

Now we can plug in 1 for y in the second equation and get:

x=2(1)-1

x=1

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Help me pls imma fail

Answers

Answer:

-

Step-by-step explanation:

what is 9 less than 3 times f

Answers

It is 3f - 9

So you multiply f by 3 and subtract 9
As simple as that!

FLOORING Miguel is putting hardwood flooring in a hallway that measures 4 feet by 17 feet. The wood he has chosen is $5.48 per square foot

What is the range of the actual cost of putting the flooring in the hallway?

OA) $316.47 and $372.64

OB) $372.64 and $431.55

O C) $362.64 and $382.64

OD) $316.47 and $431.55

Answers

A I think yup it's A good luck

Step-by-step explanation:

Miguel is putting hardwood flooring in a hallway that measures 4 feet by 17 feet. The wood he has chosen is $5.48 per square foot

What is the range of the actual cost of putting the flooring in the hallway?

OA) $316.47 and $372.64

OB) $372.64 and $431.55

O C) $362.64 and $382.64

OD) $316.47 and $431.55

aaaaaaaaaaaaaaaaaaaa

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Answer:

what grade are you??..........

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Answer:

justin biberis black

Step-by-step explanation:

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Answer:

10/1 or 10

Step-by-step ex planation:

The rate of change is just a fancy word for slope!

To find the slope of this line I found two points of the graph that were easy to determine.  Slope = rise/run

which is this case was rise 10 because the point went from 20 to 30 and the run being 1 because it was going from 1 to 2

Hope this helps!!

Please tell me if I have messed up!!

I enjoy learning from my mistakes:)

Simply using quadratic formula! Brainliest will be awarded if correct

Answers

Answer:

[tex]\left \{ {{y1=-1.2+0.4i} \atop {y2=-1.2-0.4i}} \right.[/tex]

Step-by-step explanation:

5y + 12 = [tex]\frac{-8}{y}[/tex]

y*(5y+12)=-8

5[tex]y^{2}[/tex] + 12y = -8

5[tex]y^{2}[/tex] + 12y + 8 = 0

Δ(Delta) = [tex]b^{2}[/tex] - 4ac

= [tex]12^{2}[/tex] - 4*5*8

= -16

Δ<0

therefore we have complex number

y = [tex]\frac{-b}{2a}[/tex] ± [tex]\frac{\sqrt{|Delta|} }{2a}[/tex]

[tex]\left \{ {{y1=-1.2+0.4i} \atop {y2=-1.2-0.4i}} \right.[/tex]

What will be the result when each term sin2theta+cos2theta =1 is divided by sin2theta

Answers

Answer: Did you copy and paste this because this just hits different. message me if i misunderstood this.

Step-by-step explanation:

the length of 2x metres and it's width is 2 metres shorter than its length. what is the area of the rectangle​

Answers

Answer:

4x^2-4x

Step-by-step explanation:

2x*(2x-2)

(2x)(2x)+(2x)(−2)

[tex]4x^2-4x[/tex]

Hope this helped! :)

Find the area of a trapezoid with height h and bases b1 and b2.

h=6 in.

b1=9 in.

b2=11 in.

Answers

The answer is the following

9+11 = 20
20/2 = 10
10 x 6 = 60

Hey y’all,please help me :)

Answers

Answer:

-c-4≥8

Step-by-step explanation:

Just ask!

Hope this helps. :)

find the equation of the line with slope of 2 passing through (3,1)

Answers

Answer:

y = 2x - 5

Step-by-step explanation:

Find the product z1z2 in standard form. (Simplify your answer completely.)
z1 = 9 + 3i, z2 = −9 + 3i

Answers

Answer:

See image

Step-by-step explanation:

These are "complex numbers" because they have the imaginary number, i, in the expression.

The 9 (and the -9) is the real part and the 3i is the imaginary part. But when you add or subtract, multiply or divide them you can manipulate them just as if the i was a variable (like x or n or y) If you learned to multiply

(x+2)(x+5)

= x^2 + 7x + 10

This problem will work the same way. You may have learned "FOIL" or using a box to multiply two binomials (two-piece things like x+2)

**SUPER IMPORTANT NOTE: i^2 is equal to -1

These particular complex numbers are called conjugates which means they have the same 'pieces' the 9 and the 3i, with only one sign different. So there is a short cut for this problem and the imaginary number falls out and we get a real number answer. This doesn't happen for every question, only when you multiply conjugates, but the method shown here works for multiplying complex numbers all the time.

find the side of square whose perimeter. is 24.8cm.​

Answers

Answer:

6.2

Step-by-step explanation:

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