The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

OCR C3 (not MEI) Official Thread - Tuesday 21st June 2016

Scroll to see replies

Original post by SGHD26716
Are you sure you are doing OCR. You could be OCR MEI


Original post by hallo.C
Are you definitely on the right thread here? I have never seen anything about proof before FP1 in any of my OCR text books.


Yeah I'm definitely not doing MEI and it's at the end of C3 in this textbook (A2 version though I could only find a pic of the AS one)?? I was thinking it was strange there weren't any past paper questions on it so maybe they've just put it in the book even though it's not in the spec idk why they would do that though

Posted from TSR Mobile
(edited 7 years ago)
1464128446218.jpg18.0KB
Couldn't find an official thread so thought I'd make one:h:

How is everyone finding it? Are you prepared?

Resources:
http://www.ocr.org.uk/qualifications/as-a-level-gce-mathematics-3890-3892-7890-7892/
http://www.physicsandmathstutor.com/a-level-maths-papers/c3-ocr/
Reply 22
Avatar for S.G.
S.G.
22
Original post by TheTopStudent
Couldn't find an official thread so thought I'd make one:h:

How is everyone finding it? Are you prepared?

Resources:
http://www.ocr.org.uk/qualifications/as-a-level-gce-mathematics-3890-3892-7890-7892/
http://www.physicsandmathstutor.com/a-level-maths-papers/c3-ocr/


A thread already exists: http://www.thestudentroom.co.uk/showthread.php?t=3994965
Looks like this thread is dying; going to attempt to get it back up...

Here's a lovely question from June '10 that is a good example of OCR putting in traps to test your mathematical awareness (you'll see it when you check the mark scheme for this question...).

Screen Shot 2016-06-18 at 10.36.55.png
Hey guys! does anyone know why if an answer to an equation is always positive that means it has two roots? the question i'm talking about that had this situation is https://www.youtube.com/watch?v=S-qI58gPEfA&list=PLJNWih4EmO5Xyq24i1cqKOdr5bwFqtN2_&index=21

all i can think is that if the discriminant is positive then it has two real roots but im not sure how the discriminant is involved in this question? :smile:
Original post by buckeybarnes
Hey guys! does anyone know why if an answer to an equation is always positive that means it has two roots? the question i'm talking about that had this situation is https://www.youtube.com/watch?v=S-qI58gPEfA&list=PLJNWih4EmO5Xyq24i1cqKOdr5bwFqtN2_&index=21all i can think is that if the discriminant is positive then it has two real roots but im not sure how the discriminant is involved in this question? :smile:




if tan^2 = a positive number,

tan^2 -[a positive number] = 0

so discriminant (b^2-4ac) would be 0^2-(4)*(1)*(-[a positive number]) which always equals a positive number

so there are 2 roots.
(edited 7 years ago)
Reply 26
Avatar for duncant
duncant
2
Original post by buckeybarnes
Hey guys! does anyone know why if an answer to an equation is always positive that means it has two roots? the question i'm talking about that had this situation is https://www.youtube.com/watch?v=S-qI58gPEfA&list=PLJNWih4EmO5Xyq24i1cqKOdr5bwFqtN2_&index=21

all i can think is that if the discriminant is positive then it has two real roots but im not sure how the discriminant is involved in this question? :smile:

I am assuming you mean at the end when she rights tan^20=a positive number?

that is because if you then square root that positive number, you get x/- the positive number, thus two roots
Original post by klosovic
if tan^2 = a positive number,

tan^2 -[a positive number] = 0

so discriminant (b^2-4ac) would be 0^2-(4)*(1)*(-[a positive number]) which always equals a positive number

so there are 2 roots.


Nice method! However, will you need to draw a graph of some description to show that there are two solutions within the given range? (will have a look at m.scheme when I get back home).
Original post by klosovic
if tan^2 = a positive number,

tan^2 -[a positive number] = 0

so discriminant (b^2-4ac) would be 0^2-(4)*(1)*(-[a positive number]) which always equals a positive number

so there are 2 roots.


that kinda makes sense thank you!
Original post by klosovic
if tan^2 = a positive number,

tan^2 -[a positive number] = 0

so discriminant (b^2-4ac) would be 0^2-(4)*(1)*(-[a positive number]) which always equals a positive number

so there are 2 roots.


so the tan^2 is the squared term, there is no B term because there isn't a tan and the number without a tan is (a positive number) ? super interesting way to do it!!
Original post by duncant
I am assuming you mean at the end when she rights tan^20=a positive number?

that is because if you then square root that positive number, you get x/- the positive number, thus two roots


thank you :smile:
Reply 31
Avatar for danroar
danroar
Original post by rebirth61213
Looks like this thread is dying; going to attempt to get it back up...

Here's a lovely question from June '10 that is a good example of OCR putting in traps to test your mathematical awareness (you'll see it when you check the mark scheme for this question...).

Screen Shot 2016-06-18 at 10.36.55.png



How is this supposed to trap you, is it part iii ? I thought that was quite a OCR classic by now :P
Original post by danroar
How is this supposed to trap you, is it part iii ? I thought that was quite a OCR classic by now :P


Do the question, check the mark scheme. You'll see it... (well, it made me go "ohhhhhh" at least)...
Reply 33
Avatar for S.G.
S.G.
22
Original post by rebirth61213
Do the question, check the mark scheme. You'll see it... (well, it made me go "ohhhhhh" at least)...


Yeah I got 5/16 pi. Good question. Something you can't just put in the graphics calculator and get an answer
Original post by SGHD26716
Yeah I got 5/16 pi. Good question. Something you can't just put in the graphics calculator and get an answer


the answer is 1/36 pi.... (for part iii)
Reply 35
Avatar for msulli
msulli
2
Anyone have the 2015 paper and MS
Ahhh I need to make sure I get 90+ tomorrow, the nerves have kicked in!
Original post by SGHD26716
Are you sure you are doing OCR. You could be OCR MEI


In theory questions requiring proof by contradiction or disproof by counterexample can be set in any of the A2 units.

In practice, such questions have never been set, except in last Friday's FP3 paper. That was the first time I've ever seen proof by contradiction appear on an OCR maths paper.

Original post by msulli
Anyone have the 2015 paper and MS


Paper: http://static1.squarespace.com/static/52c1f91ee4b0a77a50337e61/t/56bf9e6b2fe1311b18cf8441/1455398653328/OCR+C3+June+2015.pdf
Mark scheme: http://static1.squarespace.com/static/52c1f91ee4b0a77a50337e61/t/56bf9e8d2fe1311b18cf850e/1455398666618/OCR+C3+June+2015+mark+scheme.pdf
(edited 7 years ago)
Reply 38
Avatar for msulli
msulli
2
Original post by marioman
In theory questions requiring proof by contradiction or disproof by counterexample can be set in any of the A2 units.

In practice, such questions have never been set, except in last Friday's FP3 paper. That was the first time I've ever seen proof by contradiction appear on an OCR maths paper.



Paper: http://static1.squarespace.com/static/52c1f91ee4b0a77a50337e61/t/54c7fb3fe4b03741e3cb35d4/1422397438473/OCR+C3+June+2014.pdf
Mark scheme: http://static1.squarespace.com/static/52c1f91ee4b0a77a50337e61/t/56bf9e8d2fe1311b18cf850e/1455398666618/OCR+C3+June+2015+mark+scheme.pdf


Thanks but thats the 2014 paper
Original post by msulli
Thanks but thats the 2014 paper


I've just updated my post with the link to the 2015 paper.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you