1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Bogdan [553]
3 years ago
15

Solve the following differential equation using using characteristic equation using Laplace Transform i. ii y" +y sin 2t, y(0) 2

, y'(0) 1
Mathematics
1 answer:
kifflom [539]3 years ago
3 0

Answer:

The solution of the differential equation is y(t)= - \frac{1}{3} Sin(2t)+2 Cos(t)+\frac{5}{3} Sin(t)

Step-by-step explanation:

The differential equation is given by: y" + y = Sin(2t)

<u>i) Using characteristic equation:</u>

The characteristic equation method assumes that y(t)=e^{rt}, where "r" is a constant.

We find the solution of the homogeneus differential equation:

y" + y = 0

y'=re^{rt}

y"=r^{2}e^{rt}

r^{2}e^{rt}+e^{rt}=0

(r^{2}+1)e^{rt}=0

As e^{rt} could never be zero, the term (r²+1) must be zero:

(r²+1)=0

r=±i

The solution of the homogeneus differential equation is:

y(t)_{h}=c_{1}e^{it}+c_{2}e^{-it}

Using Euler's formula:

y(t)_{h}=c_{1}[Sin(t)+iCos(t)]+c_{2}[Sin(t)-iCos(t)]

y(t)_{h}=(c_{1}+c_{2})Sin(t)+(c_{1}-c_{2})iCos(t)

y(t)_{h}=C_{1}Sin(t)+C_{2}Cos(t)

The particular solution of the differential equation is given by:

y(t)_{p}=ASin(2t)+BCos(2t)

y'(t)_{p}=2ACos(2t)-2BSin(2t)

y''(t)_{p}=-4ASin(2t)-4BCos(2t)

So we use these derivatives in the differential equation:

-4ASin(2t)-4BCos(2t)+ASin(2t)+BCos(2t)=Sin(2t)

-3ASin(2t)-3BCos(2t)=Sin(2t)

As there is not a term for Cos(2t), B is equal to 0.

So the value A=-1/3

The solution is the sum of the particular function and the homogeneous function:

y(t)= - \frac{1}{3} Sin(2t) + C_{1} Sin(t) + C_{2} Cos(t)

Using the initial conditions we can check that C1=5/3 and C2=2

<u>ii) Using Laplace Transform:</u>

To solve the differential equation we use the Laplace transformation in both members:

ℒ[y" + y]=ℒ[Sin(2t)]

ℒ[y"]+ℒ[y]=ℒ[Sin(2t)]  

By using the Table of Laplace Transform we get:

ℒ[y"]=s²·ℒ[y]-s·y(0)-y'(0)=s²·Y(s) -2s-1

ℒ[y]=Y(s)

ℒ[Sin(2t)]=\frac{2}{(s^{2}+4)}

We replace the previous data in the equation:

s²·Y(s) -2s-1+Y(s) =\frac{2}{(s^{2}+4)}

(s²+1)·Y(s)-2s-1=\frac{2}{(s^{2}+4)}

(s²+1)·Y(s)=\frac{2}{(s^{2}+4)}+2s+1=\frac{2+2s(s^{2}+4)+s^{2}+4}{(s^{2}+4)}

Y(s)=\frac{2+2s(s^{2}+4)+s^{2}+4}{(s^{2}+4)(s^{2}+1)}

Y(s)=\frac{2s^{3}+s^{2}+8s+6}{(s^{2}+4)(s^{2}+1)}

Using partial franction method:

\frac{2s^{3}+s^{2}+8s+6}{(s^{2}+4)(s^{2}+1)}=\frac{As+B}{s^{2}+4} +\frac{Cs+D}{s^{2}+1}

2s^{3}+s^{2}+8s+6=(As+B)(s²+1)+(Cs+D)(s²+4)

2s^{3}+s^{2}+8s+6=s³(A+C)+s²(B+D)+s(A+4C)+(B+4D)

We solve the equation system:

A+C=2

B+D=1

A+4C=8

B+4D=6

The solutions are:

A=0 ; B= -2/3 ; C=2 ; D=5/3

So,

Y(s)=\frac{-\frac{2}{3} }{s^{2}+4} +\frac{2s+\frac{5}{3} }{s^{2}+1}

Y(s)=-\frac{1}{3} \frac{2}{s^{2}+4} +2\frac{s }{s^{2}+1}+\frac{5}{3}\frac{1}{s^{2}+1}

By using the inverse of the Laplace transform:

ℒ⁻¹[Y(s)]=ℒ⁻¹[-\frac{1}{3} \frac{2}{s^{2}+4}]-ℒ⁻¹[2\frac{s }{s^{2}+1}]+ℒ⁻¹[\frac{5}{3}\frac{1}{s^{2}+1}]

y(t)= - \frac{1}{3} Sin(2t)+2 Cos(t)+\frac{5}{3} Sin(t)

You might be interested in
he radioactive element​ carbon-14 has a​ half-life of 5750 years. A scientist determined that the bones from a mastodon had lost
elena-s [515]

Answer:

The bones were 12,485 years old at the time they were​ discovered.

Step-by-step explanation:

Amount of the element:

The amount of the element after t years is given by the following equation, considering the decay rate proportional to the amount present:

A(t) = A(0)e^{-kt}

In which A(0) is the initial amount and k is the decay rate, as a decimal.

The radioactive element​ carbon-14 has a​ half-life of 5750 years.

This means that A(5750) = 0.5A(0), and we use this to find k. So

A(t) = A(0)e^{-kt}

0.5A(0) = A(0)e^{-5750k}

e^{-5750k} = 0.5

\ln{e^{-5750k}} = \ln{0.5}

-5750k = \ln{0.5}

k = -\frac{\ln{0.5}}{5750}

k = 0.00012054733

So

A(t) = A(0)e^{-0.00012054733t}

A scientist determined that the bones from a mastodon had lost 77.8 ​% of their​ carbon-14. How old were the bones at the time they were​ discovered?

Had 100 - 77.8 = 22.2% remaining, so this is t for which:

A(t) = 0.222A(0)

Then

0.222A(0) = A(0)e^{-0.00012054733t}

e^{-0.00012054733t} = 0.222

\ln{e^{-0.00012054733t}} = \ln{0.222}

-0.00012054733t = \ln{0.222}

t = -\frac{\ln{0.222}}{0.00012054733}

t = 12485

The bones were 12,485 years old at the time they were​ discovered.

8 0
3 years ago
Help please. I attempted, but I couldn't succeed.
german

Answer:

y=(3/2)x+-14

First blank: 3

Second blank:2

Last blank:-14

Step-by-step explanation:

The line form being requested is slope-intercept form, y=mx+b where m is slope and b is y-intercept.

Also perpendicular lines have opposite reciprocal slopes so the slope of the line we are looking for is the opposite reciprocal of -2/3 which is 3/2.

So the equation so far is

y=(3/2)x+b.

We know this line goes through (x,y)=(4,-8).

So we can use this point along with our equation to find b.

-8=(3/2)4+b

-8=6+b

-14=b

The line is y=(3/2)x-14.

3 0
3 years ago
What is the slope of the line that passes through the points (4, 10)(4,10) and (1, 10) ?(1,10)? Write your answer in simplest fo
ikadub [295]

Answer:

0

Step-by-step explanation:

Slope = Δy/Δx

Slope = 10-10/4-1

Slope = 0/3

Slope = 0

It is a Horizontal Line

-Chetan K

6 0
2 years ago
May you help me with this question please
Lostsunrise [7]

Answer:

<em>Option C</em>

Step-by-step explanation:

Consider each of these graphs. Let us formulate an inequality for each of them, and match the one with an inequality of x > - 14.5;

Graph 1, x > 13.5\\Graph 2, x \geq 14\\Graph 3, x > 14.5\\Graph 4, x \geq 15

Graph 3 is the only one that matches with the inequality provided to us.

* Note that shaded circles are represented by a greater / less than or equal to, and non - shaded circles are represented by a greater / less than sign.

<em>Solution ⇒ Graph 3</em>

5 0
3 years ago
Read 2 more answers
A Boxerville Express commuter train leaves the station every 30 minutes. When Theo arrives at the station, a woman tells him she
Dmitrij [34]
Answer: D

The answe is just simply D because of the minutes when it adds up is almost the same as MPH
4 0
3 years ago
Read 2 more answers
Other questions:
  • Two samples of fish from a pond were analyzed. The second sample was taken six months after the first sample.
    11·2 answers
  • Which situation best represents causation?
    7·2 answers
  • The product of three binomials, just like the product of two, can be found with repeated applications of the distributive proper
    9·1 answer
  • Two trains leave stations 238 miles apart at the same time and travel toward each other. One train travels at 95 miles per hour
    6·1 answer
  • Which fraction represents the decimal 0.8888...?
    6·2 answers
  • Carmen used a random number generator to simulate a survey of how many children live in the households in her town. There are 1,
    15·1 answer
  • A bag contains 7 red, 4 blue, and 6 white marbles.
    15·1 answer
  • PLS ANSWER CORRECTLY
    10·1 answer
  • PLS HELP!! BRAINLIEST WILL BE REWARDED!!!
    13·1 answer
  • Can choose two answers!
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!