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Edexcel A2 C4 Mathematics June 2015 - Official Thread

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They didn't say that? They said

\displaystyle sec^2(y) = \frac{2}{cos(2y)+1}

ImageUploadedByStudent Room1434206885.755949.jpg

By implication, this suggests that they are referencing cos^2(y), right?

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Reply 1001

rayquaza17

Original post by kingaaran

By implication, this suggests that they are referencing cos^2(y), right?

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I think monii was incorrect when they said about integrating cos^2(y) because you can actually integrate that, but you don't have to do that in this question. (Sorry monii)

Post 993 has the correct answer for this question.

Reply 1002

NikolaT

Original post by kingaaran

By implication, this suggests that they are referencing cos^2(y), right?

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Not sure how well this has come out by hope it's of use.

Photo0104.jpg176.4KB

Reply 1003

crashMATHS

Original post by rayquaza17

To rectify, the only way to integrate

cos^2(y)

is by using the double angle formulae, or is there another 'FP3' method?

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Reply 1004

crashMATHS

Original post by NikolaT

Not sure how well this has come out by hope it's of use.

Oh, you were talking about the integral of 1/cos^2(y) :redface:

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Reply 1005

rayquaza17

Original post by kingaaran

To rectify, the only way to integrate

cos^2(y)

is by using the double angle formulae, or is there another 'FP3' method?

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Yes only sensible way is the double angle formula. :smile:

I can think of only one other way to integrate it, but that involves complex numbers which is FP2. Tbh I think the double angle formula is easier in this case. :tongue:

Reply 1006

JamGrip

Hi, can anyone tell me how to do 6(a) from Solomon A? The markscheme isn't very helpful. (not sure why 2sin3xsin2x = cosx-cos5x)

Thanks.

Reply 1007

NikolaT

Original post by JamGrip

Hi, can anyone tell me how to do 6(a) from Solomon A? The markscheme isn't very helpful. (not sure why 2sin3xsin2x = cosx-cos5x)

Thanks.

cos(x) = cos(3x - 2x)
cos(5x) = cos(3x + 2x)

Does that help?

Reply 1008

RobHunter97

So I'm thinking I got 69 + method marks on the C3 paper, so what do people think I'll need roughly for the A*? Aiming for low-mid 60s I think to be safe

Reply 1009

username1162972

Original post by RobHunter97

So I'm thinking I got 69 + method marks on the C3 paper, so what do people think I'll need roughly for the A*? Aiming for low-mid 60s I think to be safe

Depends on the paper bro

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Reply 1010

RobHunter97

Original post by physicsmaths

Depends on the paper bro

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Obviously, but I mean approximately. 50s, 60s etc.

Reply 1011

anonwinner

Original post by RobHunter97

Obviously, but I mean approximately. 50s, 60s etc.

60s

Reply 1012

RobHunter97

Original post by anonwinner

60s

Thank you

Reply 1013

TeeEm

Original post by kingaaran

To rectify, the only way to integrate

cos^2(y)

is by using the double angle formulae, or is there another 'FP3' method?

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by parts is another way ...

Reply 1014

mdc96

Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks

Reply 1015

TeeEm

Original post by mdc96

Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks

check by differentiation ...

Reply 1016

RobHunter97

Original post by mdc96

Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks

If you differentiate ln(6x), it becomes 6/6x which cancels to 1/x. Therefore 6x must become 6ln(x) if you integrate

Reply 1017

the bear

Original post by rayquaza17

Yes only sensible way is the double angle formula. :smile:

I can think of only one other way to integrate it, but that involves complex numbers which is FP2. Tbh I think the double angle formula is easier in this case. :tongue:

no... you can use integration by parts...in a cunning way