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Edexcel A2 C4 Mathematics June 2015 - Official Thread watch

1. (Original post by gabbons)
Are there any variations they could give on finding the volume of a solid formed when rotated by 2pi? Could they say 3pi? lol
It just seems a little shady to go to the effort of saying rotated about 2pi etc when it's not too relevant, as you just use pi*integral of y^2 :/
I think they could but if i'm not wrong you could just adjust your answer at the end

so if it was just rotated by pi then the answer would be half of if it was rotated 2 pi i think
2. Does anyone know what are the formula for area and volume of different shapes that we are expected to know.
e.g. trapezium cone etc..
3. (Original post by Leking9)
Attachment 428659C4, June 2014 (R), Q8c.)

'Find the value of t at this point' - The mark scheme has skipped some steps so i'm a bit confused right now
Express it in the form Rsin(x-α)
4. (Original post by Raizel)
Does anyone know what are the formula for area and volume of different shapes that we are expected to know.
e.g. trapezium cone etc..
All the ones from gcse. I think in some questions, they tell you that the volume of a cone is ... (Eg, I think there's a question like that in the june 2014 paper)

5. How would you integrate this without differentiating it first?
6. (Original post by Gome44)
Express it in the form Rsin(x-α)
Oh wow, cheers! I don't think that I would've ever noticed that
7. (Original post by ridirahman)

How would you integrate this without differentiating it first? because differentiating first and then integrating seems too long..
Employ the standard substitution, I believe.
8. (Original post by Paraphilos)
Employ the standard substitution, I believe.
but wouldn't you use subtst. when there are two x constants multiplied together? how can you use it here?
9. (Original post by Leking9)
Attachment 428659C4, June 2014 (R), Q8c.)

'Find the value of t at this point' - The mark scheme has skipped some steps so i'm a bit confused right now
Square the whole equation, youll get

16sin^2t= 16cos^2t - 8cost +1
then using sin^2t=1-cos^2t create a quadratic equation, then use the quadratic formula to find your values of t.
10. (Original post by ridirahman)

How would you integrate this without differentiating it first?
I had a try at it, excuse my lovely handwriting.
Attached Images

11. (Original post by ridirahman)
but wouldn't you use subtst. when there are two x constants multiplied together? how can you use it here?
I don't quite understand what you mean - could you just explain what you mean by 'two x constants multiplied together'? Regardless, under the substitution the integral in question is transformed into:

Do you see why?
12. (Original post by Raizel)
I had a try at it, excuse my lovely handwriting.
Ohh I get itttt thaaaanks! really helpful
13. (Original post by ridirahman)
Ohh I get itttt thaaaanks! really helpful
No problem m8.
14. Anyone got any suggestions for difficult vector questions from past papers?
15. (Original post by Leking9)
Oh wow, cheers! I don't think that I would've ever noticed that
You can also use tan half angles if you're feeling exotic
Anyone got any suggestions for difficult vector questions from past papers?
Draw a diagram
17. (Original post by Dante991)
Can someone help me out with this? Its June 2005 question 4 - I think I'm doing it right but can't seem to integrate
You had 1/cos squared x, which you should have changed to sec squared x ,and tbe integral of that is tan
18. (Original post by Gome44)
Draw a diagram
A diagram? Which paper was that on?
19. (Original post by ridirahman)

How would you integrate this without differentiating it first?
Like this
Attached Images

A diagram? Which paper was that on?
For every vectors question you can draw a diagram, normally makes it quite easy

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