maths question (1 Viewer)

[kooltrainer]

a locus maths question:

A is a point where the circle with equation x^2 + y^2 = 16 cuts the x axis. Find the locus of the midpoints of all chords of dis circle dat contain point A. (i think there r 2 point As )

The answer: x^2+y^2-4x = 0


also, farout, i failed my maths prelims.. got 77% .. everyone got higher than me.. im thinking my teacher deliberatly gave my low marks (do u think its possible?) . Well , she hates me. She dun listen to wot i say, she wount giv me class sheets and when i ask her to do so, she tells me off saying that if i dun respect her, she wouldnt respect me. I dun listen to her in class coz i no the stuff already and jus do my own work in class.. wot kinda teacher is that..

i didnt get my maths paper back yet.. damn

anyways, help me with the maths question

 

[genril]

kooltrainer, I have good news and bad news.

The good news is that you didn't fail your maths prelim.

The bad news, however, is that you failed basic arithmetic.

 

[Jachie]

Hahahaha "the teacher deliberately gave me wrong marks in a mathematics exam! I can see her bias shining through here!" Babe, you "failed" (except not really, 77% isn't bad at all) because you weren't listening in class. Stop acting like a poo and grow up and listen to your teacher, I'm sure your marks will improve.

 

[kooltrainer]

i no i no, that was jus sum side information.. now could sum1 help me with tht question please??

 

[ssglain]

a locus maths question:

A is a point where the circle with equation x^2 + y^2 = 16 cuts the x axis. Find the locus of the midpoints of all chords of dis circle dat contain point A. (i think there r 2 point As )

The answer: x^2+y^2-4x = 0

Let y = 0 to solve for the x-intercepts of the circle.
.: A is (±4, 0)

Now let B(h, k) be a point on the circle, so that AB forms a chord. Let M be the midpoint of AB.
.: M is [(h ± 4)/2, k/2]

i.e. The locus of M is defined by this set of parametric equations:
x = (h ± 4)/2 ...(1)
y = k/2 ...(2)
where, since B(h, k) lies on the circle, h² + k² = 16

From (2),
y² = k²/4
y² = (16 - h²)/4 ...(3)

From (1),
2x = h ± 4
h = 2(x ± 2) ...(4)

Put (4) in (3)
y² = [16 - 4(x² ± 4x + 4)]/4
y² = [16 - 4x² ± 16x - 16]/4
y² = -x² ± 4x

.: Loci of M are x² + y² ± 4x = 0

Notice that x² + y² - 4x = 0 is the locus of M if you had taken A(4, 0)

Feel free to ask for further clarification.

 

[z600]

dont blame the teacher....students vs. teachers, the teacher often wins

 

[S1M0]

dont blame the teacher....students vs. teachers, the teacher often wins

I've learnt that fact the hard way.

 

[genril]

I've learnt that fact the hard way.

Why am I not surprised...

 

[iEdd]

Besides, it is the teachers who have the weapons of maths instruction.

 

[iEdd]

Well actually that was a maths teacher's joke, which I rank slightly above science-teacher jokes.

 

[Jachie]

My Year 9 science teacher was really funny. I sometimes sit in on Physics lessons cause I'm kind of in love with him

EDITED BECAUSE SOMETIMES LEAVING WORDS OUT RESULTS IN YR WHOLE SENTENCE MAKING MUCH LESS SENSE THAN IT OTHERWISE WOULD

 

[rishika]

heya.. umm wot mathz do yoo do? lyk 2 or 3 unit?
yea my mathz teacher used 2 h8 me 2 & wen i got my 1st mathz paper bak (in term 1) i cud tell dat i deserved more markz nd that teacher had taken markz off coza spite!!
1st hava look at ur test paper and b sure that she took markz off.. if u think she has , then itz reali unfair.. so talk 2 it abt sum1 like mathz head teacher.
my mathz teacher duznt hate me anymore cuz i started 2 work reali hard at my maths.. i figured out that she hated me because i wasnt listening in class.. and givin me a lo mark waz her way of punishin me 4 this..
4 prelimz i studied reali hard nd managed to get good markz.. u do the smae and prove 2 ur teacher u can do it.. my half yearly mark 4 three unit was 60%. my prelim 3u mark was 95%. c wott hard wrk can do?
as 4 the mathz question i got no idea!! we havent finished doin locus yet soz!!