I understand what you have done but there are more terms in the question though, it's question 2 from the June 2013 (R) paper, therefore wouldn't I have too log all the other terms or something

Reply 944

rayquaza17

17

Original post by Computing7788

I understand what you have done but there are more terms in the question though, it's question 2 from the June 2013 (R) paper, therefore wouldn't I have too log all the other terms or something

Ooo this was the exam I actually sat. :biggrin:

Yes there are more terms, but you can just do the differentiation term by term.
So differentiate

3^{x-1}

,

xy

,

-y^2

, and

5

separately then add the differentiated terms all together again at the end.

Reply 945

karishmachabria

2

In the trapezium rule, is 'n' the number of strips?

Reply 946

InOrbit

9

Original post by Computing7788

A nice trick is to write that as:

e^{ln(3^{x-1})}

Bring the power down in the log:

e^{(x-1)ln(3)}

Then differentiate exponentials as normal with ln(3) being the constant

d/dx = ln(3)e^{(x-1)ln(3)}[br]= ln(3)3^{x-1}

Reply 947

Maths degree

11

can someone help me with june 13 replacement paper. Q4b ? i understand what they done in the mark scheme, but why couldn't i have taken out (10,000)^1/3 as this would lead me to still getting x=0.81 and that is still valid ? as x is less than 8/9? i tried this way and multiplied (10,000)^1/3 at end to the expansion too but dont get the same answer, get something like 24... ? pls can someone help, this is driving me crazy! many thanks

Reply 948

Moniii16081997

1

How would you integrate 2 / cos(2y) + 1
With respect to y.
Thanks

Posted from TSR Mobile

Reply 949

usycool1

19

Original post by Moniii16081997

How would you integrate 2 / cos(2y) + 1
With respect to y.
Thanks

Posted from TSR Mobile

Is that:

\dfrac{2}{\cos(2y) + 1}

or

\dfrac{2}{\cos(2y)} + 1

?

Reply 950

Moniii16081997

1

Original post by usycool1

Is that:

\dfrac{2}{\cos(2y) + 1}

or

\dfrac{2}{\cos(2y)} + 1

?

The first one

Posted from TSR Mobile

Reply 951

math42

20

Original post by Moniii16081997

The first one

Posted from TSR Mobile

Use the double angle formula for cos2y

Reply 952

usycool1

19

Original post by Moniii16081997

The first one

Posted from TSR Mobile

Ok - use the double angle formula for cos2y to rewrite it (use cos y instead of sin y). Then see if you can go on from there.

Reply 953

Joseph.S

10

I am really panicking for C4, any advice?

Reply 954

Moniii16081997

1

Original post by usycool1

Ok - use the double angle formula for cos2y to rewrite it (use cos y instead of sin y). Then see if you can go on from there.

But I don't think you can integrate
cos^2 (y)

Posted from TSR Mobile

Reply 955

toddmcnugget

7

Original post by Joseph.S

I am really panicking for C4, any advice?

Bump I'm terrible at C4 (struggling with bronze papers atm) but I need an A from this :L

Reply 956

Artfanatic

12

Original post by Moniii16081997

But I don't think you can integrate
cos^2 (y)
Posted from TSR Mobile

Can you not just make is (cosy)^2 and then integrate ?

Reply 957

Moniii16081997

1

Original post by Artfanatic

Can you not just make is (cosy)^2 and then integrate ?

I don't think you can do that, that only works when you differentiate.

Posted from TSR Mobile

Reply 958

dominicwild

6

Original post by Moniii16081997

I don't think you can do that, that only works when you differentiate.

Posted from TSR Mobile

It becomes

\dfrac{2}{2\cos^2y}

Which you then make:

\dfrac{1}{\cos^2y} = \sec^2y

(edited 8 years ago)

Reply 959

Maths degree

11

Original post by 1 8 13 20 42

Use the double angle formula for cos2y

can someone help me with june 13 replacement paper. Q4b ? i understand what they done in the mark scheme, but why couldn't i have taken out (10,000)^1/3 as this would lead me to still getting x=0.81 and that is still valid ? as x is less than 8/9? i tried this way and multiplied (10,000)^1/3 at end to the expansion too but dont get the same answer, get something like 24... ? pls can someone help, this is driving me crazy! many thanks. Do you mind helping me out pls :smile:

Edexcel A2 C4 Mathematics June 2015 - Official Thread

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