AQA A2 Mathematics Pure Core 4 MPC4 - 17th June 2016

Scroll to see replies

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...'??

Reply 21

RockyG

Original post by Ryhana

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

Reply 22

Berke0

What we gonna do lads.. Lol what we gonna do

Reply 23

Ryhana

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?

Reply 24

CasioGamer98

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.

(edited 7 years ago)

Reply 25

Ryhana

Original post by CasioGamer98

Thank you!
I still need to get my head round these things before tomorrow or I'm screwed along with vectors...

Reply 26

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.

Reply 27

JDMason

Original post by joebush

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.

Reply 28

geeza007

Original post by fpmaniac

Anyone can answer this question:
Prove
$\frac{cosx}{1-tanx} + \frac{sinx}{1-cotx} = sinx + cosx$

and

$(cotx + cosecx)^2 = \frac{1+cosx}{1-cosx}$

I got this. Im certain about my first answer but the second is probably wrong

1466085373284-527187735.jpg482.2KB

Reply 29

Examguy123

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?

Reply 30

JamieLW

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).

Reply 31

Mowerharvey

If you had something like 2sin(x) + 3cos(x) = 1.5, could you use Rsin/cos(x +/- y) ?

Reply 32

CasioGamer98

ImageUploadedByStudent Room1466091042.375202.jpg

Posted from TSR Mobile

Reply 33

Ano123

Original post by Mowerharvey

If you had something like 2sin(x) + 3cos(x) = 1.5, could you use Rsin/cos(x +/- y) ?

Yes.

Reply 34

Ano123

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.

Reply 35

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

Reply 36

-jordan-

Original post by Ryhana

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.