IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: Recko on May 11, 2010, 08:16:53 am

Title: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 08:16:53 am: Hey Guys

I'm Going to start with myself first, please oct/nov 05, question 9 part iii

i've found out that tan x= gradient, where x is the angle between the line and the x-axis is that correct?

if so, then why do you find the difference between the two angles anyways?

thanks in advance
Title: Re: Math P1 Questions/Predictions
Post by: nipuna92 on May 11, 2010, 08:45:57 am: Because you have to find the angle between the 2 lines
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 08:46:32 am: hold i'll get you the post...I've answered this before
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 08:47:18 am: https://studentforums.biz/index.php/topic,6531.120.html

Here
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 09:07:15 am: THANK YOU SO MUCH! =D
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 09:18:52 am: no problem :)
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 09:41:55 am: I have another question

oct/nov 06
question 9 i) & ii)

:)
Title: Re: Math P1 Questions/Predictions
Post by: Padapop on May 11, 2010, 09:46:30 am: or you could try vector method.

I use it and i find it easier, though some ppl might find it weird.

The tip is to use your gradient as a vector. Then u dot product them.
Title: Re: Math P1 Questions/Predictions
Post by: nipuna92 on May 11, 2010, 10:27:46 am: can u show the dot product thing here
Title: Re: Math P1 Questions/Predictions
Post by: Padapop on May 11, 2010, 10:40:33 am: oh..

so for example, if the first line's gradient is = 2. that would be 1i + 2j. And the second line's gradient is 3/2, that would be 2i + 3j.

(1i + 2j) . (2i + 3j) blah blah blah the dot product formula.

U could try it, but i think nid's one is standard mark scheme thing, so that way is more standard. Ull get the same answer thou.
Title: Re: Math P1 Questions/Predictions
Post by: nipuna92 on May 11, 2010, 10:43:02 am: Quote from: Padapop on May 11, 2010, 10:40:33 am
oh..

so for example, if the first line's gradient is = 2. that would be 1i + 2j. And the second line's gradient is 3/2, that would be 2i + 3j.

(1i + 2j) . (2i + 3j) blah blah blah the dot product formula.

U could try it, but i think nid's one is standard mark scheme thing, so that way is more standard. Ull get the same answer thou.

thanx got it ;) ;)
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 11:29:01 am: Guys, i finished all papers,and i cracked every single question! and i know everything!

what do you think i should do now?
Title: Re: Math P1 Questions/Predictions
Post by: astarmathsandphysics on May 11, 2010, 11:32:12 am: Start P2
Jump for joy
Write to your President. He's a Nutter.
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 11:38:59 am: hahaha start P2? i still didnt do the exam sir :P and no thanks ill pass :P

hahaha my president?

sir can you please help me out in oct/nov 06 question 9 i) and ii)
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 11:56:30 am: What am i here for ? ;)

9)total surface area=200

10xy(the 2 sides) + 24x²(the 2 triangles)=200

10xy=200-24x²
y=200-24x²/ 10x

ii) V= 12x²y (area of cross-section into length) Area of cross section=area of triangle and length=y

now from the above eqn we know y=200-24x²/ 10x

substitute this in V

12x²(200-24x²/ 10x)

this gives 240x-28.8x³
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 12:11:26 pm: i get the sides part, but i dont understand the triangles one, and you dont take the upper side because its open right?

thanks! you rock ;)
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 12:16:11 pm: Area of the triangle is 1/2 bh

base is 8
half base is 4

drop a perpendicular on the base. you get 2 right angle triangles. Use Pythagoras rule to find the height.

h= $\sqrt(5^2-4^2)$
=3

so area of the triangle= 1/2 X 8 X 3= 12cm2
since there are 2 it will be=2X12=24cm2

Yes you don't take the top cuz it's open..

lol...Thank You :P
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 12:21:48 pm: i thought it was going to be like that but then i saw it was only three marks i changed my mind haha :P

thanks again

good luck to you :)
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 12:23:07 pm: You're welcome. :)

Wish you the same :)
Title: Re: Math P1 Questions/Predictions
Post by: Recko on May 11, 2010, 12:23:40 pm: by the nid404, did you finish all papers? because i almost finished every single thing and im just solving again and going through my silly mistakes( -.- ) lol
what you think i should do?
Title: Re: Math P1 Questions/Predictions
Post by: astarmathsandphysics on May 11, 2010, 12:24:56 pm: here
Title: Re: Math P1 Questions/Predictions
Post by: nid404 on May 11, 2010, 12:28:13 pm: Quote from: Recko on May 11, 2010, 12:23:40 pm
by the nid404, did you finish all papers? because i almost finished every single thing and im just solving again and going through my silly mistakes( -.- ) lol
what you think i should do?

I'm reading through the textbook and going through examples cause im done with papers too
Title: Re: Math P1 Questions/Predictions
Post by: cashem'up on May 11, 2010, 01:30:09 pm: hey sir astarmathsandphysics do u have some wicked tough tough and extra tricky questions for AS level P1 maths that could really work the mind cos i even i have done all the papers thx ;D
Title: Re: Math P1 Questions/Predictions
Post by: astarmathsandphysics on May 11, 2010, 01:58:07 pm: here
Title: Re: Math P1 Questions/Predictions
Post by: Padapop on May 11, 2010, 04:51:56 pm: didnt finish the papers :s,

thou P1 is really really simple :), all i want is that 75 hehe.

oh and theres thinking skills for me tmmr, wow bummer.