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OCR Core 2 - 22nd May

Haruhi

2sin^2x = 2- (root 3)cosx

you use the identity sin^2x + cos^2x = 1 to find sin^2x
sin^2x = 1 - cos^2x

you substitute this into the equation to turn it all to cos x

so

2(1-cos^2x) = 2 - (root 3)cos x
2-2cos^2x = 2 - (root 3)cos x

get all the cos x on one side and numbers on the other side.

(root 3)cosx + 2cos^2x = 0

let cosx = Y

2(y^2) + root3 (Y) = 0

a = 2 b=root3 c=0

-root3 +- squareroot of (3-0) all divided by 4

-root3 + root3 all over 4 = 0
-root3 - root3 all over 4 = - root3 / 2

cos-1 0 = 90
cos-1 -root3 / 2 = 150

OMG I JUST PROVED MYSELF WRONG O__O. I am such an idiot! >< I probably punched in the wrong numbers T__T

it was cos -1 (root3/2)
which is 30

Reply 101

Andylol

14

Can someone go through how they did

7^x = 2^{x+1}

That was the only question on the paper that I was totally stuck on, not a clue! Got x to be 1.81 ¬_¬

Reply 102

Graham22

definite_maybe

I got something like 2750.

yep i got 2750 aswell

Reply 103

Maximald

Pretence

does any1 remember what they got for the sum of the first 50 terms ? ( 2nd part of that question - a= 6, d=2 )

Was it 149?

Reply 104

QED

11

definite_maybe

I got something like 2750.

a = 6
d = 2

S = 25(12 + 98) = 25 x 110 = 2750

****.

Reply 105

Graham22

Maximald

Was it 149?

nope .. i got 2750 when a=6 and d=2 using 1/2n(2a+(n-1)d) formula

Reply 106

Ejit

5

Graham22

nope .. i got 2750 when a=6 and d=2 using 1/2n(2a+(n-1)d) formula

I think 149 was the answer for the geometric progression.

Reply 107

chioco

Andylol

Can someone go through how they did

7^x = 2^{x+1}

That was the only question on the paper that I was totally stuck on, not a clue! Got x to be 1.81 ¬_¬

using log laws.
xlog 7 = (x+1) log 2
x log 7 = xlog 2 + log2
x log 7 - xlog 2 = log 2
x(log 7 - log 2) = log 2
so x = log 2/(log 7 - log 2)
which gives x = 0.553

Reply 108

*Mathematician*

The paper was difficult at times but overall okay.

Mr M is a school teacher so he will not be able to post the answers up until about 4-5pm.

That's why I'm going to play Need for Speed Undercover on PS3 until then... :cool:

I really want to see these answers though... :yep:

Reply 109

SabreT

4

definite_maybe

I got something like 2750.

Yeah, thats what I got too. I think it was a decent paper overall, although I completely messed up the perimeter question, and only ended up finding the length r and moved on to the next question. What a horrible lapse !

My answers are the same as the majority of people here, so hopefully I did well.

Reply 110

damek

if my answers weren't to 3 significant figures, how many marks would i lose??

Reply 111

Ejit

5

damek

if my answers weren't to 3 significant figures, how many marks would i lose??

1 for each time, probably.

Reply 112

socksy

dannycarr1

6. dy/dx of a curve = 3x^2 + a where a is a constant
crosses at coords: (-1, 2) and (2, 17)

Can someone quickly explain this 8 marker?
I couldnt see how to do it at all :/

Substitute one take away the other...

Why on earth was it worth an entire 8 marks? I pretty much ****** up the log questions too, and I'm not sure why - didn't go so bad in revision... Does anyone remember what they were? Would be nice to check on wolfram|alpha or something.

Reply 113

Maximald

*Mathematician*

The paper was difficult at times but overall okay.

Mr M is a school teacher so he will not be able to post the answers up until about 4-5pm.

That's why I'm going to play Need for Speed Undercover on PS3 until then... :cool:

I really want to see these answers though... :yep:

I agree

there is no point refreshing this thread every 5 minutes like I have been doing :rolleyes:

hehe

Reply 114

*Mathematician*

Maximald

I agree

there is no point refreshing this thread every 5 minutes like I have been doing :rolleyes:

hehe

I'm a really good thinker you see... :cool:

Why else would I get 11 on that last question in Core 1 and do pretty well today I hope... :yep:

Reply 115

definite_maybe

4

Ejit

1 for each time, probably.

I don't think you would. The front said to 3 sig fig or to a suitable figure. As long as you didn't copy out the entire calclulate figure, you should only lose marks for when it was specifically stated to be 3 sig fig.

Reply 116

gspot92

i rekon i got about 60/72. any1 no roughly the boundaries for an A

Reply 117

Ejit

5

definite_maybe

I don't think you would. The front said to 3 sig fig or to a suitable figure. As long as you didn't copy out the entire calclulate figure, you should only lose marks for when it was specifically stated to be 3 sig fig.

Sorry, that's what I thought he meant.

If you use fractions or surds your answers are obviously more accurate, so you'd get those marks, and yeah as long as you include some decimals you should get marks for being close(or more accurate).

Reply 118

raj_mostwanted

guys i did like every single pastpaper for this CORE 2 but i think it was the hardest paper ,,,, does any1 think that grade bounderies should become lower for this paper i knw i lost abt 18 marks garunteeed

Reply 119

Graham22

raj_mostwanted

guys i did like every single pastpaper for this CORE 2 but i think it was the hardest paper ,,,, does any1 think that grade bounderies should become lower for this paper i knw i lost abt 18 marks garunteeed

same.. i did every past paper and was getting high 80s and 90 % everytime
i hope the boundaries are lowered

OCR Core 2 - 22nd May

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