Core 3 Proof OCR

I am stuck on a question from January 2013 C3 OCR paper.
It's question 9. (i)
It reads:
Prove that cos²(x+45) - 1/2(cos2x - sin2x) = sin²x.

I have gotten up to the point where sinxcosx = sin²x (I think)

Please help!

Reply 1

black1blade

19

Be super careful with your brackets and squaring brackets as that is incorrect. I made a few mistakes doing it but spotted em and it sorted its self out in the end.

Reply 2

baznoy

16

Yeah I agree with @black1blade. I remember doing this question in class a few months ago and it was very easy to make mistakes with squaring out the bracket. I think this is probably the hardest proof question I've seen for OCR.

Reply 3

black1blade

19

Original post by baznoy

Yeah I agree with @black1blade. I remember doing this question in class a few months ago and it was very easy to make mistakes with squaring out the bracket. I think this is probably the hardest proof question I've seen for OCR.

Yeah can you remember how many marks it is? Knowing our luck, there will probably be a harder one than that in our exam.

Reply 4

baznoy

16

Original post by black1blade

Yeah can you remember how many marks it is? Knowing our luck, there will probably be a harder one than that in our exam.

It was 4 marks I believe.. probably, yeah. Both looking forward to and dreading the exam tuesday!

Reply 5

GGHarambe

7

What do you think will be harder this year C3 or C4? They always seem to make 1 core exam hard like last year with C1

Reply 6

black1blade

19

Original post by GGHarambe

What do you think will be harder this year C3 or C4? They always seem to make 1 core exam hard like last year with C1

I feel like core 3 is generally harder than c4. C4 is mostly just methods but c3 has a bit more problem solving.

Core 3 Proof OCR

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you