**HL Maths P2 Before/After

patrickkelly wrote: »

Anybody get Alpha= 44Degreees and Beta=100Degrees for part (i) of question 8?

I got this also.. Quite complicated.. Used cosine rule twice and ended up having to add to angles to get alpha

DepoProvera wrote: »

I got this also.. Quite complicated.. Used cosine rule twice and ended up having to add to angles to get alpha

Ya i was the same! ended up getting beta to be most effected by the 1% error by using circles, and found that when beta is greater the 90degrees, that the 1% effects beta more, but when beta was less then 90 degrees, the 1%effects alpha more, all by use of circles and displacement along an arc!
Any body agree?

patrickkelly wrote: »

Ya i was the same! ended up getting beta to be most effected by the 1% error by using circles, and found that when beta is greater the 90degrees, that the 1% effects beta more, but when beta was less then 90 degrees, the 1%effects alpha more, all by use of circles and displacement along an arc!
Any body agree?

Woop same man!

cocopopsxx wrote: »

How did everyone go about doing the probability long question?

I got .31 for the first part.. For 2nd and 3rd I originally thought it was conditional prob but it wasn't? 2nd was straightforward and 3rd I subtracted those who were neither Arrear or Negative Equity and then subtracted those who were negative eq from that value to find total arrear(12 thousand something) my answer for part 3 was like .9 something!

Again. Anyone get root2 as K for Q3? I know my method's right but I'm pretty sure my actual answer is wrong.

patrickkelly wrote: »

And for the final part? Did u draw a circle radius 12 from centre Q, and then draw a line PQ, where this line intersected the circle, from the point 0,0 drew 2 semi circles from these points to the x-axis, and shaded the region between them?

Centre P you mean? I drew an arc of 12 around then a smaller arc for the Q.. It have me a sort of rainbow and I shaded in the inside.. However it's just dawned on me that it should have gone below the x axis aswell damnnit!

DepoProvera wrote: »

Centre P you mean? I drew an arc of 12 around then a smaller arc for the Q.. It have me a sort of rainbow and I shaded in the inside.. However it's just dawned on me that it should have gone below the x axis aswell damnnit!

ya i cant remember the points now exactly but i got that rainbow shape aswell!
In regards the x-axis, your told Alpha has a maximum of 180degrees, as does beta, so therefore it will never go bellow the x-axis?

or am I incorrect?

DepoProvera wrote: »

What did everyone get for the % increase of rejected batteries? I am never sure if percent increase is a figure like 120% .. mine was 27% increase or something close to that

I got 29 but I got the part (i) wrong

My answers (The Ones I remember)

1) Yes, it's a parallelogram, found midpoint between AD and BC and they were the same.

2) K is something like 2+root(2) or 1+root(2), can't remember. I solved it using geometry and trigonometry

3) Alpha is 45" and Beta is 80", I think. Oh and I use the "Store as letters" function on my SHARP El-W531, so that figure is either exactly accurate or wrong.

4) The last question, I think it ends up as a half-donut shape, looking like it has a piece bitten off it and a round end at one side. Hard to explain.

5) The percentage change in the "rejected coins" rate, I got to be something like 94%. That is, the 1% increased to something like 2%, hence the "rate" itself went up by 94%.

That's all I can remember for now. Maybe I'll post again later.

patrickkelly wrote: »

Just realised my mistake now, 2 semi circles of radius 12 should be drawn drom where the point Q hits the x-axis, going bellow the x-axis

But surely if alpha was 0 degrees and beta was 90 degrees it would go below?

DepoProvera wrote: »

That's what I thought in the exam but if alpha is 0 or 180 then beta could extend the arm below the x axis? I hope we are right anyway!

Ya i see that now! and there is a semi circle missing aswell at the right hand side of (0.0)! and under that there is another semi circle

Could somebody post a scanned copy of the exam please (assuming you are exempt from Irish paper 1 of course!!).

mathstalk wrote: »

My answers (The Ones I remember)

1) Yes, it's a parallelogram, found midpoint between AD and BC and they were the same.

2) K is something like 2+root(2) or 1+root(2), can't remember. I solved it using geometry and trigonometry

3) Alpha is 45" and Beta is 80", I think. Oh and I use the "Store as letters" function on my SHARP El-W531, so that figure is either exactly accurate or wrong.

4) The last question, I think it ends up as a half-donut shape, looking like it has a piece bitten off it and a round end at one side. Hard to explain.


5) The percentage change in the "rejected coins" rate, I got to be something like 94%. That is, the 1% increased to something like 2%, hence the "rate" itself went up by 94%.

Got mostly the same as these with exception to the drawing of that doughnut shaped graph, I can see where i went wrong on it though!


the " circles which had a common point (4,7), question 5 >I THINK< did anybody get x+2y=18 for the equation of this line?

DepoProvera wrote: »

Yeah I think I got that..just got slope between centres, common chord was perpindicular then just used y-y1 formula

Ya spot on, did u just draw it to prove that thet were touching?

patrickkelly wrote: »

Ya spot on, did u just draw it to prove that thet were touching?

Nah I just got distance between centres and radii of both circles.. Subtracted or added can't remember but it worked out