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Edexcel A2 C4 Mathematics June 2015 - Official Thread

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Original post by Leking9
image.jpgC4, 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) :smile:
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) :smile:
untitled.JPG

How would you integrate this without differentiating it first?
(edited 8 years ago)
Original post by Gome44
Express it in the form Rsin(x-α) :smile:


Oh wow, cheers! I don't think that I would've ever noticed that
Original post by ridirahman
untitled.JPG

How would you integrate this without differentiating it first? because differentiating first and then integrating seems too long..


Employ the standard substitution, u=6x+1u = 6x + 1 I believe.
(edited 8 years ago)
Original post by Paraphilos
Employ the standard substitution, u=6x+1u = 6x + 1 I believe.


but wouldn't you use subtst. when there are two x constants multiplied together? how can you use it here?
Reply 1366
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Terk
8
Original post by Leking9
image.jpgC4, 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.
Original post by ridirahman
untitled.JPG

How would you integrate this without differentiating it first?


I had a try at it, excuse my lovely handwriting.
IMG_20150615_110940.jpg403.5KB
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 u=6x+1u = 6x + 1 the integral in question is transformed into:

3∫1251udu3\displaystyle\int_1^{25} \dfrac{1}{\sqrt{u}}du

Do you see why?
Original post by Raizel
I had a try at it, excuse my lovely handwriting.


Ohh I get itttt thaaaanks! really helpful :smile:
Original post by ridirahman
Ohh I get itttt thaaaanks! really helpful :smile:


No problem m8.
Anyone got any suggestions for difficult vector questions from past papers?
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 :wink:
Original post by Faded-Pi
Anyone got any suggestions for difficult vector questions from past papers?


Draw a diagram
Reply 1374
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Dandz
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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
Original post by Gome44
Draw a diagram


A diagram? Which paper was that on?
Reply 1376
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GENTE
Original post by ridirahman
untitled.JPG

How would you integrate this without differentiating it first?

Like this
maths.jpg20.4KB
Original post by Faded-Pi
A diagram? Which paper was that on?


For every vectors question you can draw a diagram, normally makes it quite easy :smile:
Original post by Gome44
For every vectors question you can draw a diagram, normally makes it quite easy :smile:


Oh, I see. Thanks :smile:
Original post by ridirahman
untitled.JPG

How would you integrate this without differentiating it first?



Honestly, the best way would be to use the chain rule - much quicker & there's a smaller chance of making any silly errors

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