* Maths paper 2 (Ordinary) tips / discussion / aftermath * (1 thread only please)

dodgybarnet · 13-06-2011 02:19AM

Ficheall, if you dont mind could you help us with 2010 Q3 (b) (i) (ii) and (c)

Ficheall · 13-06-2011 04:04AM

Hmm... I don't teach geometry - I hate this stuff.
But I think...

i)

c and l intersect where both values are satisfied so you can solve by subbing one value into the other (as mentioned elsewhere on here at some stage this evening)
x^2+y^2=17
x-4y-17=0

so x=4y+17 at T
subbing this into the equation for the circle:
(4y+17)^2+y^2=17

16y^2+136y+289+y^2=17
17y^2+136y+272=0
Factorise:
Using your -b formula is probably the handiest.
a=17 b=136 c=272
(-136+/- sqrt(18496-18496))/34= -4.

Then if y=-4, subbing in to
x=4y+17 gives x=-16+17 = 1.
So the point is (1,-4).
(We can verify this is on the circle by subbing into x^2+y^2=17.
1^2+(-4)^2=17.

ii)
We know that the other end of the diameter must be directly on the opposite side of the centre of the circle - so all we have to do is to find the centre of the circle.

The internet informs me that
"The standard equation of a circle with center C(h,k) and radius r is as follows:(x - h)^2 + (y - k)^2 = r^2"
In our case h=0 and k=0 (otherwise we would have x and y coefficients as well as the x^2 and y^2. r^2=17 so r=sqrt(17).

[So just to check, we can see if the distance between the radius and our point is sqrt(17) - this is not necessary for the question, but it will put my mind at ease. Distance between (1,-4) and (0,0) is sqrt(1^2+ (-4)^2)=sqrt(17). Awesome.]

Directly opposite (1,-4) through the origin is going to be simply (-1,4).. and this is your other end-point.

Ficheall · 13-06-2011 04:13AM

c)

i)
The equation of our circle is x^2+(y-7)^2=100.
As stated above:
"The standard equation of a circle with center C(h,k) and radius r is as follows:

(x - h)^2 + (y - k)^2 = r^2

So the centre of our circle is (0,7), and the radius is 10 (the square root of 100).

ii)
The point (6,h) is on the circle.
Which means filling in 6 and h instead of x and y respectively in the equation of our circle will enable us to solve for h.

x^2+(h-7)^2=100
6^2+(h-7)^2=100
36+(h-7)^2=100
(h-7)^2=64
h-7=8 or h-7=-8

h=15 or h=-1.

Hope that helps and isn't too late!

I'll be glad when this LC nonsense is over - I'm getting terribly tired of logging onto the internet with the express intention of looking for porn, and instead ending up doing maths...

WhiskeyGoblin · 13-06-2011 06:53AM

Wait nevermind I got it!
Any pro tips for Vectors?

TheFullDuck · 13-06-2011 11:24AM

Out there :pac: a nice paper again I thought. Linear prog. the line, area and volume, stats and probability q's were all very handy!
Well at least I never have to find the length of an imaginary line again!!

Aoifums · 13-06-2011 12:07PM

Very nice paper! I was delighted

Q1 - Doss! Aced it.
Q2 - c ii was tricky but I got it in the end. I think

Q3 - Grand. I fecked up my graph first time round but I got it in the end. Finding p and q was the good kind of tricky.
Q5 - Fine until the end. Finding x was odd but I love that kind of question. I had to guess to get it but it worked out for me in the end.
Q6 - Fine, nothing remarkable.
Q7 - Same. My ogive looked a bit weird though

Q11 - I blanked on how to write the three inequalities. I made something up, not sure how right/wrong it was.

Overall it was pretty good. I had to turn one piece of graph paper sideways to draw a half decent graph. I left a nice little apology note to the corrector

In purple!

Sunny!! · 13-06-2011 12:21PM

The best paper anyone could have expected:D. Q1,2 grand q3 bit tricky trig nice just beautiful:D

amortentia · 13-06-2011 12:26PM

It was fine, but was it me or was part b of the trigonometry a bit confusing? The diagram said the opposite side was 6 but the sin ratio it gave indicated it was 3?

Gavarn · 13-06-2011 12:34PM

amortentia wrote: »

It was fine, but was it me or was part b of the trigonometry a bit confusing? The diagram said the opposite side was 6 but the sin ratio it gave indicated it was 3?

Yeah I thought that was weird.. I just multiplied the 5 at the bottom by 2 aswell to get 10 for the H.. don't know if thats what you are supposed to do but :rolleyes: oh well...

Nice paper though! 95% of it was fine!

flyaway. · 13-06-2011 12:34PM

Not bad, I guess. Question 1 was easy. Question 2 went okay. I messed up question 3 but still attempted it all. Question 6 was so simple- I kept wondering if I was missing something! Question 7 was also fine but I messed up question 9. What did everyone get for the standard deviation in question 7?

Aoifums · 13-06-2011 12:53PM

Gavarn wrote: »

Yeah I thought that was weird.. I just multiplied the 5 at the bottom by 2 aswell to get 10 for the H.. don't know if thats what you are supposed to do but :rolleyes: oh well...

Nice paper though! 95% of it was fine!

That's what I did. It was a large 3,4,5 triangle. So it was 6,8,10. Handy little question, not sure how they wanted us to prove anything so I just pointed that out. I know from previous marking schemes, you don't need to prove anything if it is a 3,4,5 sider as they assume you know what that is.

Gav77 · 13-06-2011 12:56PM

Sweet enough paper

lisabisa · 13-06-2011 02:14PM

Very happy with that paper,

.

Think I messed up the standard deviation but the method was there so I'll get some marks.

FlawedGenius · 13-06-2011 03:23PM

Can anyone tell me how many marks out of 600 do you need to get the minumum pass?? I think its 240 is it?? I wrote my answers on the exam paper from paper 2 and Im dying to see the answers now!!

Gercakeage · 13-06-2011 03:44PM

Christ paper two was so much better than paper one!!

Hope i pass now :rolleyes:

:rolleyes:

martyllia · 13-06-2011 04:44PM

loved area & volume question! and the line,vectors,stats was nice too
circle and trig bit tricky but still fine

much more better than paper 1 !!

Smartly Dressed · 13-06-2011 05:37PM

Somehow managed to botch part B of linear programming, my strongest question. Bye bye A1.

Damo 2k9 · 13-06-2011 06:10PM

Was getting a bit confused on that myself, when i got the x value i subbed it in for y

Which meant i wasnt getting the proper point of intersection but i re read it and got it sorted thank god.

Over all i thought it was a grand paper, at least everything we though was going to come up did unlike paper 1 where first principles and long division didnt come up

Fbjm · 13-06-2011 06:21PM

A!!! GOT AN A! WHAT a paper!!

babynice · 13-06-2011 06:43PM

In the middle of paper 2 I realised that I never put the question number on any of my graphs in paper 1. I left the graphs in the with the corresponding questions but does this matter?

shelbourneTID · 13-06-2011 06:44PM

Delighted I'll never have to sit a maths test again.

xaoifsx · 13-06-2011 06:44PM

with the triangle question regarding the sin 3/5 was there a mistake in th paper..or did i seriously just go dumb?? because sin 3/5 meant that the 6 was wrong on the opposite site.. does anyone have any clue about this question? someone said something about a double sided triangle or soemthing...im not sure.. any help??

xaoifsx · 13-06-2011 06:45PM

babynice wrote: »

In the middle of paper 2 I realised that I never put the question number on any of my graphs in paper 1. I left the graphs in the with the corresponding questions but does this matter?

they'll probably figure it out. they arent that lazy..they are trying to give the most marks they can..esp after the crappy paper on friday!!

J_E · 13-06-2011 06:46PM

xaoifsx wrote: »

with the triangle question regarding the sin 3/5 was there a mistake in th paper..or did i seriously just go dumb?? because sin 3/5 meant that the 6 was wrong on the opposite site.. does anyone have any clue about this question? someone said something about a double sided triangle or soemthing...im not sure.. any help??

How I interpreted it was that if the triangle says 6, that's double 3, so the 5 must be a 10 on the triangle. It's like 6/10=3/5.

I'm worried about the last part of the line and circle question, they messed me up bad.

xaoifsx · 13-06-2011 06:49PM

Cydoniac wrote: »

How I interpreted it was that if the triangle says 6, that's double 3, so the 5 must be a 10 on the triangle. It's like 6/10=3/5.

I'm worried about the last part of the line and circle question, they messed me up bad.

...oh.. darn it that made sense..i wrote a lil note saying why i think its wrong.. i did kinda think that for a second now that i remember but i just then forgot about doing that.. oh well..
ya the last bit of the line messed me up!! i didnt do the circle question because i dont like circles..but i did 5 outta 6 questions though.

probablity question was so easy and i can't get my head around it at all!! so lucky!!
loved the vectors question too..
all in all a very good paper

J_E · 13-06-2011 06:50PM

I forgot my compass so I had to draw the circle freehand. It was obviously wrong anyway

galwayman17.. · 13-06-2011 06:51PM

Cydoniac wrote: »

How I interpreted it was that if the triangle says 6, that's double 3, so the 5 must be a 10 on the triangle. It's like 6/10=3/5.

I'm worried about the last part of the line and circle question, they messed me up bad.

ya i thats how i read it too. yeah part i couldnt get the two points D so i attempted it get the attempt marks!

soccymonster · 13-06-2011 06:54PM

Regards probability actually..... I was gonna do it as a last resort because it's either wrong or right and i usually get it wrong

. But ended up doing it as an extra question anyways. But was it ridiculousy easy? Coz like.. I had it done in 5 minutes (and im abit edgy about it now coz it was too easy..or i did it wrong :P )

xaoifsx · 13-06-2011 06:56PM

soccymonster wrote: »

Regards probability actually..... I was gonna do it as a last resort because it's either wrong or right and i usually get it wrong . But ended up doing it as an extra question anyways. But was it ridiculousy easy? Coz like.. I had it done in 5 minutes (and im abit edgy about it now coz it was too easy..or i did it wrong :P )

im excatly the same!! i usually can't do it but i did it with perfection today!:D

xaoifsx · 13-06-2011 06:58PM

Cydoniac wrote: »

I forgot my compass so I had to draw the circle freehand. It was obviously wrong anyway

someone asked our examiner if he had a compass during the exam really loudly..and the examiner was like.. why would i have a compass!! and then he went around to people searching for a compass!! our examiner talks so much.. like more than the few words in the beginning and end.. and he just random stuff in between and were like shhhhh!! haha!! i think a super intendant came into our exam today..he looked pretty important!!

* Maths paper 2 (Ordinary) tips / discussion / aftermath * (1 thread only please)

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