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

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Answers

Answer:

37, 79, 7

Step-by-step explanation:

f(6) = 6² -6 +7

36-6+7 is 37

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Step-by-step explanation:

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

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Answers

The answer is the following

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It is 3f - 9

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Step-by-step explanation:

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Answer:

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Step-by-step explanation:

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

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Help me pls imma fail

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Answer:

-

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

Find the product z1z2 in standard form. (Simplify your answer completely.)
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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

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= 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)

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Answer:

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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

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Answer:

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Step-by-step explanation:

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Answer:

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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

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

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Δ<0

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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

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Tommy took 8 donuts to work.

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Answer:

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Step-by-step explanation:

2x*(2x-2)

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

Hope this helped! :)

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ANSWER: {(
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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:

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Answers

Answer: y = -x - 3

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OA) $316.47 and $372.64

OB) $372.64 and $431.55

O C) $362.64 and $382.64

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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

Problem #3
Imagine you are building a triangular garden. Two sides of the garden measure 230 ft and
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230ft
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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:

Plot /\ABC: B(-1,-1), and C(4,-1)
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Answer:

i dont know sry

Step-by-step explanation:

:)

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Hi there! :)

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

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7

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-1

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Hope it helps!

~Answer given by

An Unknown Dreamer

Good luck.

Brendan says that the negative of - 1/3
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​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".

Hey y’all,please help me :)

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Answer:

-c-4≥8

Step-by-step explanation:

Just ask!

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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

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Hope this helps!!

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Answer:

super man

Step-by-step explanation:

aaaaaaaaaaaaaaaaaaaa

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Answer:

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Step-by-step explanation:

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

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