1993 HSC Question (1 Viewer)

[rama_v]

Hi Guys, I've got a question that I came across in the 1993 exam that I couldn't do. Its question 10.(a) I have attached a copy of the question. I could get part (ii) quite easily but for some reason I cannot get part (iii) - the answer is an exact answer:
x = (sqrt[5] -1)/2

Thanks

 

[velox]

AD = BD because of equal angles
1 - x^2 = x
x^2 + x -1 = 0
Then use quadratic formula.

http://img326.imageshack.us/img326/1223/answer8dd.jpg

 

[FinalFantasy]

using the similar triangle u proved, AB/BC= BC\DC=CA\BD
u know AB=1, BC=x
AD=x if u put in the angles properly
hence DC=1-x
BD=x as well if u put in da angles
dat gives u
1/x=x\(1-x) (using AB/BC=BC/DC)
so 1-x=x²
solve that den u should get some stuff

 

[velox]

using the similar triangle u proved, AB/BC= BC\DC=CA\BD
u know AB=1, BC=x
AD=x if u put in the angles properly
hence DC=1-x
BD=x as well if u put in da angles

dat gives u
1/x=x\(1-x) (using AB/BC=BC/DC)
so 1-x=x²
solve that den u should get some stuff

are there any questions you can't do FF ? (not specific to this question but in general, you answer every question!)

 

[FinalFantasy]

are there any questions you can't do FF ? (not specific to this question but in general, you answer every question!)

lol i can't do HEAPS, i just don't ask dem here cuz i have my private tutor
and the ones i never answer are probability ones and graph ones cuz i am so shit at dem LoL

 

[rama_v]

You must spread some Reputation around before giving it to FinalFantasy again.

 

[FinalFantasy]

You must spread some Reputation around before giving it to FinalFantasy again.

lol give it to velox he ans. it first not me
and i dun care about dis reputation thing, but thx anyway haha

 

[rama_v]

lol give it to velox he ans. it first not me
and i dun care about dis reputation thing, but thx anyway haha

lol, I gave velox a rep too thanks velox

 

[velox]

haha if only rep counted towards uai. No problem, glad i could actually do it.

 

[DeanM]

are there any questions you can't do FF ? (not specific to this question but in general, you answer every question!)

when you do solve it you get:

(root 5-1)/2