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OCR Maths C3 11th June

byebyebye

How did it go?

Was okay upto the last questions where it got very tricky..

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Reply 1

energig

I thought it went alright, i made a few stupid mistakes, reckon i got about 80%.

I managed to sneak a paper out with me, so if anyone wants to know what any of the questions were just ask.

Reply 2

**mentalheroin**

what the hell was q6 about?

Reply 3

byebyebye

for the 8) part i) question fr proving tan identities how many marks would i lose for working tan60 to be root3/2 instead of root3... i know it was a stupid mistake! But i carried on..

also for part ii) what were the solutions? i think i made it too complicated with tan^4theta etc..

Reply 4

jimmzay

I would quite like to have the questions, and also, if Mr M or anyone else is out there and would like to put up the answers, that would be muchly appreciated.

Thanks

Reply 5

byebyebye

PHKnows

what the hell was q6 about?

What draw secx and solve the equation it gave?

Reply 6

epoxi

I was aiming for 100%, but sadly that volumes of revolution one tripped me up...anyone manage to do that one? Someone told me it had something to do with "integration by parts"...which I've never heard of.

If I remember correctly (from 5 minutes ago)...

We were supposed to find the volume of the above equation between:

•

f(x)

•

x=1

•

x=e^1

•

y=0

When revolved through 4 right-angles about the X-axis.

I have no idea how to do it using the content of the C3 course!

Reply 7

**mentalheroin**

byebyebye

What draw secx and solve the equation it gave?

maybe it was 5 then. where you had to rearrange an integral to get a=.

Reply 8

byebyebye

PHKnows

maybe it was 5 then. where you had to rearrange an integral to get a=.

Oh right. well you had to integrate using the limits to get an answer with a as an unknown.. then you put it to equal 45 as it said the area = 45.

Reply 9

energig

Well i dont feel like typing out all the questions, and i dont have a scanner or anything.

Q6 was

Given that the integral of (6e^2x + x) = 42

show that a = 1/2 ln(15 - 1/6a^2)

It was worth 5 marks... easy :P although i got it wrong by integrating x as
x^2 and not 1/2x^2 :mad:

Reply 10

epoxi

byebyebye

What draw secx and solve the equation it gave?

Drawing secx is a waste of time: you had to use the cosx curve: invert the equation to make:

cosx = 1/a
instead of
secx = a

Reply 11

**mentalheroin**

epoxi

We were supposed to find the volume of the above equation between:

•

f(x)

•

x=1

•

x=e^1

•

y=0

When revolved through 4 right-angles about the X-axis.

I have no idea how to do it using the content of the C3 course!

for the volume of revo, you do y^2, then you get 4 over blah, which is equal to a sixth of the differentiated value calculated in part one. So its a sixth times the original question i think

Reply 12

**mentalheroin**

byebyebye

Oh right. well you had to integrate using the limits to get an answer with a as an unknown.. then you put it to equal 45 as it said the area = 45.

oh yeah of course. ive never seen that before

Reply 13

byebyebye

epoxi

Drawing secx is a waste of time: you had to use the cosx curve: invert the equation to make:

cosx = 1/a
instead of
secx = a

Yeah secx is just annoying to draw.. ah well easy 2 marks i guess!
i thought it rearranged to tanx=(some number)??
I Can't remember the question though..

Reply 14

epoxi

PHKnows

for the volume of revo, you do y^2, then you get 4 over blah, which is equal to a sixth of the differentiated value calculated in part one. So its a sixth times the original question i think

So basically you differentiate it instead of integrating (so you can use C3 chain rule etc.)? Damn, I should've thought of that!

Reply 15

epoxi

byebyebye

Yeah secx is just annoying to draw.. ah well easy 2 marks i guess!
i thought it rearranged to tanx=(some number)??
I Can't remember the question though..

If you're talking about the very last question, then you got:

(tanx)^2=a (where a=something with loads of (k^2)s flying around...which is a positive constant).
then
tanx=a^0.5

because a is positive and real, a^0.5 gives two roots (one positive and one negative) which will cross once each on tanx between 0 and 180.

Reply 16

**mentalheroin**

does anyone know what the grade boundaries would be

Reply 17

Ioannidesp

PHKnows

for the volume of revo, you do y^2, then you get 4 over blah, which is equal to a sixth of the differentiated value calculated in part one. So its a sixth times the original question i think