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    Can anyone explain how do we answer question 7 in the June 2013 AQA past paper? It's on forming differential equations. I don't get how to use the information like what do we do with the info 'every 12 hours...'??
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    (Original post by Ryhana)
    Can anyone explain how do we answer question 7 in the June 2013 AQA past paper? It's on forming differential equations. I don't get how to use the information like what do we do with the info 'every 12 hours...'??
    Iirc it says the max tide is 12 hours meaning when t is 12, cos(theeta) is 1, as 1 is the max value of cos
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    What we gonna do lads.. Lol what we gonna do
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    (Original post by RockyG)
    Iirc it says the max tide is 12 hours meaning when t is 12, cos(theeta) is 1, as 1 is the max value of cos
    So how do you eventually get the cos(pi/6 t) in the answer?
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    (Original post by Ryhana)
    So how do you eventually get the cos(pi/6 t) in the answer?
    The tide is said to repeat every 12 hours in the same way y=cos(x) repeats every 2pi radians. For the tide to be consistent with y=cos(x) divide 2pi by 12 and you find the constant k must be pi/6. Hence cos(pi/6 t) is now proportional to the rate of change of the tide.
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    (Original post by CasioGamer98)
    The tide is said to repeat every 12 hours in the same way y=cos(x) repeats every 2pi radians. For the tide to be consistent with y=cos(x) divide 2pi by 12 and you find the constant k must be pi/6. Hence cos(pi/6 t) is now proportional to the rate of change of the tide.
    Thank you!
    I still need to get my head round these things before tomorrow or I'm screwed along with vectors...
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    What are the best ways to revise for this exam if it is going to be similar to the core 3 exam from yesterday? Past paper revision is useless and I wondered if anybody had any advice on how to deal with the same type of unfamiliar questions? Or how to revise for them.
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    (Original post by joebush)
    What are the best ways to revise for this exam if it is going to be similar to the core 3 exam from yesterday? Past paper revision is useless and I wondered if anybody had any advice on how to deal with the same type of unfamiliar questions? Or how to revise for them.
    Thought the C3 was similar to Edexcel so have at look at their C4. Also have you done AEA/MAT/STEP? makes this stuff seem easy.
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    (Original post by fpmaniac)
    Anyone can answer this question:
    Prove


    and

    I got this. Im certain about my first answer but the second is probably wrong
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    Hows everyone feeling for tommorows core 4 exam after the core 3. What kind of questions do you think will come up? What do you think is the best way to revise for this exam?
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    (Original post by geeza007)
    I got this. Im certain about my first answer but the second is probably wrong
    Not quite, you can't cancel out the denominator as the numerator doesn't contain both parts in both sections. To cancel like that it would have to read cosx(1-cotx)(1-tanx) + sinx(1-tanx)(1-cotx).
    Here I did the first question with explanations but I can't get my head around the second one just yet. Also the image I attach seems to want to flip and I can't fix it, sorry about that (and my handwriting).Name:  IMG_2961.jpg
Views: 342
Size:  404.4 KB
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    If you had something like 2sin(x) + 3cos(x) = 1.5, could you use Rsin/cos(x +/- y) ?
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    Name:  ImageUploadedByStudent Room1466091042.375202.jpg
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    (Original post by Mowerharvey)
    If you had something like 2sin(x) + 3cos(x) = 1.5, could you use Rsin/cos(x +/- y) ?
    Yes.
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    (Original post by JDMason)
    Thought the C3 was similar to Edexcel so have at look at their C4. Also have you done AEA/MAT/STEP? makes this stuff seem easy.
    Of course STEP makes C4 look easy. But I Don't think it can be suitable for revising C4.
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    What are the ways of checking that we got the right answer? For example, you can use the integration or differentiation function of your calculators to make sure you have integrated/differentiated properly. Is there anything similar for the other topics? I'd hate to move onto another question feeling confident that my previous answer is correct...when actually I still made an error
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    (Original post by Ryhana)
    What are the ways of checking that we got the right answer? For example, you can use the integration or differentiation function of your calculators to make sure you have integrated/differentiated properly. Is there anything similar for the other topics? I'd hate to move onto another question feeling confident that my previous answer is correct...when actually I still made an error
    For partial fractions... putting a number in both sides of the it (before and after) and checking it's the same. For differential equations, just differentiate it I guess. For binomials maybe use it to estimate a value at a particular number and see if it's similar or not.
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    Predictions on vectors? Possibly a 7+ mark question? Has shortest distance ever came up in an exam question?
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    You can just tell that this year's going to have a horrendous vector question...
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    (Original post by JamieLW)
    Not quite, you can't cancel out the denominator as the numerator doesn't contain both parts in both sections. To cancel like that it would have to read cosx(1-cotx)(1-tanx) + sinx(1-tanx)(1-cotx).
    Here I did the first question with explanations but I can't get my head around the second one just yet. Also the image I attach seems to want to flip and I can't fix it, sorry about that (and my handwriting).Name:  IMG_2961.jpg
Views: 342
Size:  404.4 KB
    Oh yeah, thanks for correcting it.
 
 
 
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