Math Qns..
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Erm, this is A.Maths..
integrate (3sin x - 4cos 2x) dx
wads ur ans? -
Ans: -3 cos x - 2 sin 2x.
If you want, I can go the long way and define what is sin x and cos x and then show that the answer is as above, but seeing it's just A Maths, no need so troublesome:
Using | for integrate symbol:
Note: | sin x dx = - cos x + c where c is an arbitrary constant.
| cos 2x dx = (1/2) sin 2x + d where d is an arbitrary constant.
Therefore:
| 3 sinx - 4 cos 2x dx
= 3 | sinx dx - 4 | cos 2x dx
= - 3 cos x - 2 sin 2x + e where e is an arbitrary constant.
Guess I forgot about the constant....
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-3cos x-2sin 2xOriginally posted by FadeToBlack:Erm, this is A.Maths..
integrate (3sin x - 4cos 2x) dx
wads ur ans? -
Originally posted by CoolMyth:Ans: -3 cos x - 2 sin 2x.
i totally throw back to my teacher my A maths le u still can remember??!! -
Where is your working?Originally posted by CoolMyth:Ans: -3 cos x - 2 sin 2x.
How come no questions on Coordinate Geometery? -
u mean i was told in the first placeOriginally posted by starblue: i totally throw back to my teacher my A maths le u still can remember??!! 
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coordintate geometry i also know... it;s about one of the few maths topics i know....Originally posted by shade343:Where is your working?
How come no questions on Coordinate Geometery?
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no need workings, they are integration...Originally posted by shade343:Where is your working?
How come no questions on Coordinate Geometery? -
wda u talking about??Originally posted by FadeToBlack:u mean i was told in the first place -
working shown above already....
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Bingo, Ans: -3 cos x - 2 sin 2x that's what i worked it out...
BUT THE TYS ANS WROTE -3 COS X - 2 SIN X + C
wah lao make me work until so long then realised ans is wrong... -
u asked if i still can remember... i don't even know in the first place...Originally posted by starblue:wda u talking about??
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Wah, just to verify your tys is wrong. If you know its right, its right ok?
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i was directing it at coolmyth lah...Originally posted by FadeToBlack:u asked if i still can remember... i don't even know in the first place... -
he is maths major.Originally posted by starblue: i totally throw back to my teacher my A maths le u still can remember??!! -
I also remember, cuz I am engineer, must be responsible to the society.Originally posted by starblue:i was directing it at coolmyth lah... -
in NUS??!!Originally posted by the.raven:he is maths major. -
indeed.....i need maths to be my bread and butter in future....Originally posted by the.raven:he is maths major. -
Well, I must admit my A maths isn't really very good, so whenever there's a different ans, there's always a higher probability of me getting the ans wrong than the book's ans getting wrong...Originally posted by ditzy:Wah, just to verify your tys is wrong. If you know its right, its right ok?
oso im not very confident 1... haix.. -
dunno ask himOriginally posted by starblue:in NUS??!! -
i thought i got say what.... no meh....?Originally posted by starblue:in NUS??!! -
hai, not me???Originally posted by starblue:i was directing it at coolmyth lah... -
you did??? forgot liao..Originally posted by CoolMyth:i thought i got say what.... no meh....? -
haha.. next time see carefully mah...Originally posted by FadeToBlack:hai, not me??? 
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it's ok, dear, i only said F.O.S is a plain....maybe not explict enough....Originally posted by starblue:you did??? forgot liao..