C3 OCR (Not MEI) - Friday 12th June 2015

What would be the answer to part ii) on this question?


http://i.imgur.com/gIF3137.png

It's a many to one function so it can't have an inverse? Is that right? If so what happens if you restrict the domain to x>1.5? Surely then it has an inverse, but I can't work out what it would be.

Tricky core 3 trig question:

http://gyazo.com/6bb77b08f7dd1f6f62b3bd9c59652b72

I could do 9(i) and 9(ii) but I could not do 9(iii). If someone could kindly help me out, that would be dandy. Paper is from Jan 06 if anyone is interested. (pls halp)

What would be the answer to part ii) on this question?


http://i.imgur.com/gIF3137.png

It's a many to one function so it can't have an inverse? Is that right? If so what happens if you restrict the domain to x>1.5? Surely then it has an inverse, but I can't work out what it would be.

You can use the part at the top: Sin6theta would be = 3sin2theta-4sin2theta^3
Use this.

So at the moment you have (3sin6beta)/sin2beta=4

Sub in the sin6beta thing.

So you will have 3(3sin2beta-4sintbeta^3)/sin2beta=4

Take out a factor of sin2beta

3sin2beta(3-4sin^2beta)/sin2beta=4

Cancel the sin2beta
Giving you when expanded 9-12sin^2beta=4
12sin^2beta=5

And do the normal stuff from then. Would have sent a pic but phone is dead.

You can use the part at the top: Sin6theta would be = 3sin2theta-4sin2theta^3
Use this.

So at the moment you have (3sin6beta)/sin2beta=4

Sub in the sin6beta thing.

So you will have 3(3sin2beta-4sintbeta^3)/sin2beta=4

Take out a factor of sin2beta

3sin2beta(3-4sin^2beta)/sin2beta=4

Cancel the sin2beta
Giving you when expanded 9-12sin^2beta=4
12sin^2beta=5

And do the normal stuff from then. Would have sent a pic but phone is dead.

Actually don't worry, I am dumb xD

I could use some tips. I feel like I've gotten arrogant, a couple of months ago I could blitz any of the past papers, but I've put so much focus on FP2 that I fear that I might've started to forget C3&4, despite the fact that I genuinely believe that they are easy. What should I do?

Same, except I've put a lot of focus of FP3 as well as FP2. (Actually, every module apart from C4 and C3 because especially compared to Further Pure, they are easy).
I'm just planning to go over lots of papers.

I'd say have a scan over:
http://www.mathshelper.co.uk/OCR%20C3%20Revision%20Sheet.pdf (C3)
http://www.mathshelper.co.uk/OCR%20C4%20Revision%20Sheet.pdf (C4)
(especially if you get stuck in a paper and forget something. They're much more concise than the textbooks).

The stuff I've made mistakes on are forgetting things like the integral of f'(x)/f(x) is ln(f(x)).

Binomial expansion is easy, just make sure you make the bracket start with 1. (Apparently loads of people forget this.)

It looks like we both think exactly the same.


I will.


I managed to forget that on a FP2 paper recently, hopefully I've learned never to do that again.


I'd like to agree, but I often hesitate when I see stuff like (x^2 - x + 2)^(-1) and I sometimes forget what all the inverse graphs looks like. Hopefully I've not forgot vectors either, otherwise I think everything else is FP2 on easy mode.

Unbelievable...I'm sitting in seat C3 of the exam hall for my C3 exam.

Out of interests, how did people do part ii? Once you've seen the answer, it's easy, but prior to that I can't see anything better than trial and error.

EDIT Oh wow... nevermind, this is what I get for working on scrap paper, my graph was 1/2 pi in the wrong direction but even still this is a weird question.

Someone suggest to me some hard core 3 and 4 papers, I've done them all before but I could use the practice.

They are gonna try something different with this exam, it always happens near the end of the series. My guess it will be cosec graphs etc