Is anyone else finding C4 hard? Watch

benwellsday
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#21
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#21
Integration isn't that bad, vectors is worse (well it was for me back then, I was like "woah what the hell is a line"...good times). It just takes a lot of practice. I guess it's hard for me to judge because by that time I was about 80% through FP2 integration, which was hell, but with enough practice C4 should be the same. Learning when to use integration by parts and when to use substitution is the next most important thing after understanding how to use them.
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Simplicity
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#22
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#22
Look in the formula book.

The formula book even has the formula for intergration by parts in it.
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Seb.c
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#23
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#23
i guess this is a good thread to ask what sin^3 x integrates to.

I know you have to use the cos2x identities for sin^2 x but what about sin^3?
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benwellsday
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#24
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Split it into \int sinx (1 - cos^2 x) dx then in a seperate place differentiate  cos^3 x and see how that relates to doing the above integral.
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Simplicity
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#25
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Think cos3x.
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silent ninja
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#26
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(Original post by Seb.c)
i guess this is a good thread to ask what sin^3 x integrates to.

I know you have to use the cos2x identities for sin^2 x but what about sin^3?
clue: write sinx.sin^2(x)

I found C3 harder than C4 (neither were difficult tbh) because it took a bit longer to get to grips with trig, whereas calculus was fairly straightforward for me. If you find any areas difficult, just practice 'til you drop. That's the simplest advice
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chud101
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#27
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#27
ISIT really that hard? ive got it in june along with m2! you lot are scaring me haha
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Seb.c
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#28
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(Original post by silent ninja)
clue: write sinx.sin^2(x)
Thankyou, (cheers to the 2 above too) ok that makes quite a bit more sense now, ill go and have another go.
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silent ninja
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#29
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(Original post by chud101)
ISIT really that hard? ive got it in june along with m2! you lot are scaring me haha
Depends on ability, but it's really just a continuation-- if you found C3 and the like okay, chances are C4 will be fine too.
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Simplicity
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#30
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#30
Why do we need to learn intergration, can't computer do it?
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benwellsday
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#31
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Computers can be used to make estimates, of values of definite integrals, but computer need to be programmed by someone. Plus calculus has plenty of applications in degree level physics and above.
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Mathematician!
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#32
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(Original post by Papado)
My class started C4 the other day and it seemed pretty easy, but then i looked at intergration and i can't believe its coming. we've gotten to vectors and up to there it was a piece of cake. i can't believe theres such a jump between that and intergration.

if anyone has any revision tips for C4 or anything, post em up!!

i usually just learn something with my class on Friday, go over EVERY question in that chapter in the book over the weekend, go over any quieries with my tutor on Tuesday, and start, on my own, the next chapter so that when we get into class I'm already sort of familiar with what we'll be doing next. So far this has been going pretty well, but unfortunately, intergration is imminent.

HELP :zomg:
Seems OK. I think it takes a while to get used to, as it is a step up from C3.
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pink_cait
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#33
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Honestly, No
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Seb.c
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#34
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(Original post by benwellsday)
Split it into \int sinx (1 - cos^2 x) dx then in a seperate place differentiate  cos^3 x and see how that relates to doing the above integral.

Errrrr ive made it sinx(1/2 - 1/2cos2x)

Then tried to use y = uv rule and kinda screwed it up completely and it looks nothing like the answer given lol. Any more hints? :confused:
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benwellsday
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#35
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(Original post by Seb.c)
Errrrr ive made it sinx(1/2 - 1/2cos2x)

Then tried to use y = uv rule and kinda screwed it up completely and it looks nothing like the answer given lol. Any more hints? :confused:
 sinx (1 - cos^2 x) = sinx - sinxcos^2x
Integrating sin x is easy (I hope!). The other bit isn't so easy, but here's a trick
 \frac{d}{dx} cos^3 x = -3cos^2xsinx . Now if only there was some way to get 1/3 of that...
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Simplicity
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#36
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(Original post by benwellsday)
Now if only there was some way to get 1/3 of that...
Thats why its impossible to integrate this. I just typed it up into online intergrator and it said you can't do this.
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Vitamin Sea
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#37
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Apparently, C4 papers are pretty predictable so even though the topics are hard, I think I'll be alright if I practice loads of papers.

I find C3 questions harder tbh
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benwellsday
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#38
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You typed it in wrong, derivatives work in a way that  \frac{d}{dx} (af(x)) = a \frac{dy}{dx} when a is constant. So in this case, you set a = 1/3.
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Seb.c
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#39
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(Original post by benwellsday)
 sinx (1 - cos^2 x) = sinx - sinxcos^2x
Integrating sin x is easy (I hope!). The other bit isn't so easy, but here's a trick
 \frac{d}{dx} cos^3 x = -3cos^2xsinx . Now if only there was some way to get 1/3 of that...
ty
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Aout
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#40
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C4 wasn't too hard actually. We just finished it today (implicit differentiation was our last topic). Trust me, the integration is stupidly easy in comparison to the further maths integration we've been doing simultaneously.

If you just practise, it gets easier. Plus it helps to do a list of all the integration types, and in which order you should check it off (which is easiest for you), so that if you have a checklist, you know how to integrate everything (you don't miss out any method and get stuck).
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