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OCR MEI Maths C4 Mon01/06/2009

It was for this reason that they allowed the mistake. It was that common. Don't fear, most of the people I knew (including me) made it.

jas0nuk

Lord jayshah

jas0nuk

I know you know a lot about mark schemes, maybe you can set my mind at rest about this: I have recalled one error that I made in the quadratic on q8. When solving,

Unparseable latex formula:

\[[br]\begin{array}{l}[br] t + \sqrt 3 = \sqrt 4 \\ [br] t + \sqrt 3 = \pm 2 \\ [br] \end{array}[br]\][br]

Instead of writing the correct solutions

t = 2 - \sqrt 3 , - 2 - \sqrt 3 \\

I did something retarded and finished off with

\begin{array}{l}[br] t = 2 - \sqrt 3 ,2 + \sqrt 3 \\ [br] \tan 15 < (2 + \sqrt 3 ) \\ [br] .:\tan 15 = 2 - \sqrt 3 \\ \end{array}

When I said tan 15 < ... that was based on the calculator value. Is that even sufficient to justify the solution I took?

I know I'll lose a mark for the wrong alternative solution, but what about the rest?

Let's have a look.

Going to be honest, everything before "I did something retarded and finished off with" confuses me. Doesn't matter, as the line under is what matters, and you got there.

Now, you've stated:

\tan 15 < (2 + \sqrt 3 )

Which is mathematically sound. I put "However, only

\tan ^{-1} (2 - \sqrt{3}) = 15

(or something to that effect), so the solution is

\tan 15 = 2 - \sqrt 3

".

What you've said is fine. It said neither "without a calculator", "explain your reasoning carefully" nor anything that would imply this. It was more about obtaining a surd form for

\tan 15

, which you did elegantly and fine. You will not be debited any marks (unless, you've said something mathematically unsound, I haven't noticed and I'm so tired I probably won't until you point it out :p:

).

4 marks:
M1 - Solve quadratic
A1 - Find only valid root
M1 -

2 \pi < ...

E1 - Final solution (*, answer given).

Hope that helps.

Reply 421

jas0nuk

Ahh, thanks.

What I meant about being retarded was,

From the quadratic, if you complete the square and sq.root both sides, you end up with

t + \sqrt 3 = \sqrt 4

which, if I think about it, could actually have 4 solutions

t \pm \sqrt 3 = \pm 2

But anyway, as said the only one which is correct is

2 - \sqrt 3

and I got the right one in the end. :biggrin:

Reply 422

jayshah31

14

jas0nuk

Ahh, thanks.

What I meant about being retarded was,

From the quadratic, if you complete the square and sq.root both sides, you end up with

t + \sqrt 3 = \sqrt 4

which, if I think about it, could actually have 4 solutions

t \pm \sqrt 3 = \pm 2

But anyway, as said the only one which is correct is

2 - \sqrt 3

and I got the right one in the end. :biggrin:

Completing the square; interesting way to go about it.

I see what you mean now, but then again, I don't think they pay all that much notice to be honest. I think, at this level,

\pm \sqrt{3}

can be substituted (without being penalised) for

\sqrt{3}

, but perhaps anything above would have repercussions (i.e. AEA/Step+).

We'll just have to wait until August :smile:

Reply 423

sinesquared.

9

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah failed.

Reply 424

jayshah31

14

sinesquared.

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah failed.

If it makes you feel any better, I was going to sign-up again with the username of "1-cossquared" and say we can go together :redface:

Reply 425

Martazz

1

Don't think I've done well tbh
Was anyone else not gutted by the fact there was no binomial expansion question? They are the only questions i can ever count on to be good! haha

Reply 426

jayshah31

14

Martazz

Don't think I've done well tbh
Was anyone else not gutted by the fact there was no binomial expansion question? They are the only questions i can ever count on to be good! haha

Uhum yes, and the completely lack of depth of Differential Equations. I did an entire DE module, for what? Nothing :sigh:

Reply 427

jas0nuk

I reckon they'll realise that this paper had way too much trig and not enough binomial expansion/DE.

Reply 428

jayshah31

14

jas0nuk

I reckon they'll realise that this paper had way too much trig and not enough binomial expansion/DE.

While this is true, this is simply the synoptic nature of C4. I :live: trig, anyway :smile:

Reply 429

Bezzler

1

jayshah31

Completing the square; interesting way to go about it.

I see what you mean now, but then again, I don't think they pay all that much notice to be honest. I think, at this level,