Help with Maths please!

[Ldlian987]

Hi guys could you please help me with the Laplace transformations please? I'm really bad at it. Thanks in advance!

 

 

[Chrispie]

all returned to teacher liao....

 

to think i was able to do this laplace thingy loooooooooong time ago.. im quite impressed with myself!

[Coltplussport]

Hi guys could you please help me with the Laplace transformations please? I'm really bad at it. Thanks in advance!

 

Never seen or heard of this before!!!

[Rayleigh]

Never seen or heard of this before!!!

 

Lan Pah transform. Dun you remember? :D

[Youth92]

Hi ts, don't you have a formula book for you to refer to?

[1fast1]

Hi guys could you please help me with the Laplace transformations please? I'm really bad at it. Thanks in advance!

 

This is obviously homework. I can't post a complete solution for a problem like this (and honestly, I'm not feeling well enough to), but it should be simple enough for you to work out with a few hints.

 

The first part says you can use tables if you choose to. You don't really need to. Here's how I would do it:

 

a) i) e^(-st).e^(-2t) = e^[-(s+2)]t. Now just integrate and apply those bounds!

 

ii) The table should have an entry for sinh(at). If it only has an entry for sin(at), then use sinh(3t)= -i.sin(3it). Here I'm transforming the hyperbolic sine to a circular sine using an imaginary argument. Now you can either apply the table entry for sin(at) or use e^(iat) = cos(at) + isin(at) and do real and imaginary parts together, then split them up. Fairly standard method, you should be able to find it in the text.

 

iii) The table should have an entry for t^n. If not, you can integrate by parts twice. Trivial.

 

iv) There should be an entry for e^-at.cos(bt). I suggest you use cos(ibt) = cosh(bt) to do the transform and apply the table entry. Another way is to use cosh(bt) = 0.5*(e^(bt) + e^(-bt)), then combine exponents. This is probably the simplest way.

 

v) Another integration by parts.

 

b)i) Do a partial fraction decomposition, then compare with the Laplace transform for e^(-at). Remember the linearity of the transform, makes everything easy peasy.

 

ii) Split the fraction into 5/s + 5/s^2. The first term has an ILT of simply 5, while the second term has an ILT of simply 5t, so the overall ILT is 5(t+1).

 

c) This is a linear second order ordinary differential equation. Your text should cover this. The basic method involves taking the Laplace transform of both sides, then hoping the algebra is simple enough to allow a quick solution. There are tricks for the first and second derivatives, and linearity helps you just add all the terms. Then take the ILT.

Edited August 27, 2013 by Turboflat4

[Evillusion]

Never seen or heard of this before!!!

Lap place lar....where the lap dancer place her buttock on your lap or your face!

[1fast1]

Anyway, TS, the solution for your d.e. (the last part) is y(t) = e^(-t) + 2e^(2t).

[Mcf777]

bro.....math "sheng tong"

[1fast1]

bro.....math "sheng tong"

 

Thanks bro - er... may I ask what "sheng tong" means please? Paiseh, my Chinese is very rudimentary.

 

(I'm Indian - just in case you didn't know. )

Edited August 27, 2013 by Turboflat4

[WTF]

Thanks bro - er... may I ask what "sheng tong" means please? Paiseh, my Chinese is very rudimentary.

 

(I'm Indian - just in case you didn't know. )

direct translate is "god-child".......

[Mysportwish]

the answer is e^(u%) - d^(#.2)

 

@#^&*%@)*($^)*($^@*($^

 

what the heck is that?

[1fast1]

direct translate is "god-child".......

 

Thanks!

 

[Ender]

Thanks!

 

More accurate would be prodigy. Your math power is .

[1fast1]

More accurate would be prodigy. Your math power is .

 

Thanks bro.

[Djim]

 

Teacher arrested at JFK (攪笑)

 

 

A public school teacher was arrested today at John F. Kennedy International airport as he attempted to board a flight while in possession of a ruler, a protractor, a compass, a slide-rule and a calculator. At a morning press conference, Attorney General Eric Holder said he believes the man is a member of the notorious Al-Gebra movement.

 

He did not identify the man, who has been charged by the FBI with carrying weapons of math instruction.

 

'Al-Gebra is a problem for us', the Attorney General said. 'They derive solutions by means and extremes, and sometimes go off on tangents in search of absolute values.' They use secret code names like "X" and "Y" and refer to themselves as "unknowns" but we have determined that they belong to a common denominator of the axis of medieval with coordinates in every country. As the Greek philosopher Isosceles used to say, "There are 3 sides to every triangle."

 

When asked to comment on the arrest, President Obama said, "If God had wanted us to have better weapons of math instruction, He would have given us more fingers and toes." White House aides told reporters they could not recall a more intelligent or profound statement by the President. It is believed that another Nobel Prize will follow.

 

 

 

 

[Jamesc]

The problem with maths is math is easy but maths teachers don't know how to teach it.

 

If you need to calculate 4% of 75 then just reverse it and calculate 75% of 4.

 

It's so much easier.

 

[1fast1]

The problem with maths is math is easy but maths teachers don't know how to teach it.

 

If you need to calculate 4% of 75 then just reverse it and calculate 75% of 4.

 

It's so much easier.

 

Yes, very good insight James. Now, if we complain about paying 7% GST on necessities like a $2 loaf of bread, certain politicians will ask us to think of it as only 2% GST on a $7 loaf of bread. We should count ourselves lucky and thank our Dear Leaders!

 

Edited August 20, 2019 by Turboflat4