Maths wtf

[meghatronic]

Well for a start that result needs simplifying; it should be 2*sqrt(arcsin(x)). As for the integral, just make the substitution x = sin(u) and it all drops out nicely:

Who's awesome? You're awesome.

I completely forgot about integration by substitution.....

Only sad people post mathematics equations at 2:35 in the morning and expect a proper answer.

I wasn't bothered by the faux posts - it's what makes OcUK great.

Is it just me or does this stuff just fall out of your head as soon as you stop using it on a daily basis?

Evidently, yes!

 

[Greebo]

I did maths and further maths A level (a grades) and maths at University and I can't supply an answer (although the answer posted did make sense)

Amazing how much stuff you forget.

 

[meghatronic]

I did maths and further maths A level (a grades) and maths at University and I can't supply an answer (although the answer posted did make sense)

Amazing how much stuff you forget.

Worrying, really. 1/3 of my degree was Chemistry, and a friend of a friend asked the other day for me to check over some of their A level coursework. I didn't have a ****** clue. That £14k was well spent.....!

 

[Alex74]

Bah, woke up too late, beaten by a mile .

Best guide is that if it looks horrific, then there'll be a substitution involved I
f there are trig functions involved, or rooted brackets on the bottom of the fraction, then it'll be a trig substitution.

1/sqrt((1 - x^2)) is a very common one to watch out for with trig substitutions.

Here you easily get rid of the arccsc by subtituting x = sinu, and then the rooted bracket simplifies nicely to an easy integration.



Also we need a Latex implementation on the forums for future maths problems!

 

[meghatronic]

1/sqrt((1 - x^2)) is a very common one to watch out for with trig substitutions.

Here you easily get rid of the arccsc by subtituting x = sinu, and then the rooted bracket simplifies nicely to an easy integration.

The thing that was greatly frustrating me is I was obsessing over the differential of 1/sqrt((1 - x^2)) is arcsin x +c, but could then not see how this fitted in the puzzle! Doh.

Although I'm trying to work out how 1/ becomes cos u/ at the moment

 

[apatia77]

I remember nothing of this stuff anymore even though I was a math guru at school

 

[Fortyseven]

Although I'm trying to work out how 1/ becomes cos u/ at the moment

When you subsitute:
x = sinu
dx/du = cosu
dx = cosu du

so dx is exchanged with cosu du

 

[meghatronic]

When you subsitute:
x = sinu
dx/du = cosu
dx = cosu du

so dx is exchanged with cosu du

I just read up on integration by substitution, I like the fact one can treat "dx" as an entity. Seems cheeky

I owe lots of cookies today!

 

[Alex74]

The thing that was greatly frustrating me is I was obsessing over the integral!! of 1/sqrt((1 - x^2)) is arcsin x +c, but could then not see how this fitted in the puzzle! Doh.

Although I'm trying to work out how 1/ becomes cos u/ at the moment

substituting x = sin u then integrating wrt u means we have to switch from dx to du.
We note that
dx/du = cos u

so dx = cos u du.

Substitute in and voila!

EDIT: Damnit, beaten again

 

[meghatronic]

Substitute in and voila!

EDIT: Damnit, beaten again

Like a ginger stepchild.

Threads like this remind me:
(1) I'm not alone in forgetting things,
(2) There are always people better than you,
(3) There are always people willing to help for no gain,
(4) OcUK is a great community
and
(5) pancake.

 

[zooankski]

Is it just me or does this stuff just fall out of your head as soon as you stop using it on a daily basis? I had to do loads of calculus for Electrical & Electronic Engineering BTEC but I can't remember any of it now!

Did the same here for my aero engineering - never needed any of it in real life, hence now i struggle working out if i have been given the right change!

 

[Knubje]

I've enjoyed how many people have been useless in this thread, makes me feel better about my lack of advanced maths skills!

Hahah +1

Didn't do Maths beyond GCSE, 10 years ago.

I looked at the OP and thought to myself "I like Turtles..."

 

[CliffyBiro]

I must have been absent the day they did the X times tables.

 

[Cosimo]

I looked at the OP and thought to myself "I like Turtles..."

Understanding turtles is far more complex than that equation.

 

[aardvark]

damn this is depressing - i could have done this when i was 18 - now, i haven't got the faintest idea how to even start!

 

[Dr.EM]

Why do so many subjects insist on teaching this when it isn't relevant? It's difficult to understand for many, including me

 

[Fortyseven]

Why do so many subjects insist on teaching this when it isn't relevant? It's difficult to understand for many, including me

In chemical engineering, reaction rates and reactor science relies heavily on integration.

Might not be relevant to everyone though.

 

[Dave]

In chemical engineering, reaction rates and reactor science relies heavily on integration.

Might not be relevant to everyone though.

And then once you embark on doing Fluid Mechanics, the ability to do algebra and calculus becomes important! And quite difficult

 

[Fortyseven]

And then once you embark on doing Fluid Mechanics, the ability to do algebra and calculus becomes important! And quite difficult

Yes, easily the most difficult subject I have ever studied, due to it being so mind numbingly boring.

 

[trentlad]

Nice work D.P. and Alex74.

I was up trying to crack this one. I got as far as Trig substitution and just couldn't flip it at all. It is scary how this disappears from memory when you don't use it but I still love trying. I feel like I need to try at least, especially after going though uni and finishing maths in the top 3 of my class.