Integration (1 Viewer)

[FinalFantasy]

if u've got something like
int. sinxcosx dx
can u write it as int. sinx d(sinx)?
or r u only allowed to do it in ur head, not allowed to actually put dat down?

not sure if i can put d(sinx) cuz it looks a bit weird lol

Thx!

 

[wah]

by international standards you can, however, in Australia some teachers insist that "they haven't seen it before" and so you get marked down. BUT it is accepted in other countries. in fact students use that in the HSC assessments, and have to argue their way to their teachers and show them evidence that such "writing methods" do exist to get their marks. so in short, it is theoretically correct.

to overcome this problem, you can write:
integral of sinx [d(sinx)/dx] * dx
(since dx/dx is 1)

this is acceptable in australia =D

 

[FinalFantasy]

hmm that's annoying having to write the d(sinx)\dx thing lol

 

[shafqat]

dr pender wrote it as int. sinx d(sinx)
and he's pretty high up in the BOS maths world
so i guess u can use it

 

[FinalFantasy]

dr pender wrote it as int. sinx d(sinx)
and he's pretty high up in the BOS maths world
so i guess u can use it

ooer, juz needed someone to say dat, hahaha
im juz gonna use it now

 

[want2beSMART]

err you dont know what int. sinxcosxdx is?

 

[Slidey]

-cos(2x)/4 + C

But that's not the question.

I prefer to use. '

E.g.: The derivative of sinx is (sinx)'. Trouble is you don't know what it is with respect to. But then, that also applies to D(sinx).

And as far as I know, it is a capital D, not a lower case d. Isn't it called the differential operator or something?

Example:

d/dx of sinx = D(sinx) = cosx
Second derivative of sinx = D²(sinx) = D(cosx) = -sinx
Integral of sinx = D^-1(sinx) = -cosx + C

A common variation is having the superscript as a subscript:

D₂(sinx)

 

[ngai]

dr pender wrote it as int. sinx d(sinx)
and he's pretty high up in the BOS maths world
so i guess u can use it

...for the hsc...
but what about school assessments?...teachers mark those, and if they dont like what u write, then they take your marks away

 

[ngai]

E.g.: The derivative of sinx is (sinx)'. Trouble is you don't know what it is with respect to. But then, that also applies to D(sinx).

i suppose ' means w.r.t.x, just like y' means dy/dx
but using ' in integration...just seems a bit confusing

And as far as I know, it is a capital D, not a lower case d. Isn't it called the differential operator or something?

Example:

d/dx of sinx = D(sinx) = cosx
Second derivative of sinx = D²(sinx) = D(cosx) = -sinx
Integral of sinx = D^-1(sinx) = -cosx + C

A common variation is having the superscript as a subscript:

D₂(sinx)

he is talking about integration, where u have sinxcosxdx = sinx d(sinx), and not sinxcosxdx = sinx d(sinx)/dx

 

[shafqat]

...for the hsc...
but what about school assessments?...teachers mark those, and if they dont like what u write, then they take your marks away

thats right
well students then better know wat their teachers want

 

[Slidey]

i suppose ' means w.r.t.x, just like y' means dy/dx
but using ' in integration...just seems a bit confusing

Hell yes!

he is talking about integration, where u have sinxcosxdx = sinx d(sinx), and not sinxcosxdx = sinx d(sinx)/dx

Mmm. I sort of realised, but thought I'd add a comment on differential notation anyway. I skimmed over his first post, sorry.

 

[Captain pi]

if u've got something like
int. sinxcosx dx
can u write it as int. sinx d(sinx)?
or r u only allowed to do it in ur head, not allowed to actually put dat down?

not sure if i can put d(sinx) cuz it looks a bit weird lol

Thx!

Just say:

[int:] sin(x)cos(x) dx

= ½sin²(x) + c

Inverse Chain Rule​

That is permissible.

 

[FinalFantasy]

Just say:

[int:] sin(x)cos(x) dx

= ½sin²(x) + c

Inverse Chain Rule​

That is permissible.

can i juz write the answer w\out saying "Inverse Chain Rule"?

 

[shafqat]

yah
don't have to write reverse chain rule