barbernator
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Re: HSC 2012 Marathon 
cmon guys!!! you havent got the answer yet
cmon guys!!! you havent got the answer yet
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HSC 2012 MX1 Marathon #2 (archive) (3 Viewers)
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nightweaver066
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barbernator
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barbernator
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Re: HSC 2012 Marathon
PM me if u want a clue, or the answer to work towards
PM me if u want a clue, or the answer to work towards
nightweaver066
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Re: HSC 2012 Marathon
9.8m?
I drew the diagram wrong the first time lol.
9.8m?
I drew the diagram wrong the first time lol.
nightweaver066
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Re: HSC 2012 Marathon
Also angle 60 degrees between the 6.5 and 12.
Exactly what i used.
Also angle 60 degrees between the 6.5 and 12.
nightweaver066
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Re: HSC 2012 Marathon
So prone to silly mistakes because of the numbers involved. :S
lol.. Can't be bothered redoing.. Will do when i have time.
So prone to silly mistakes because of the numbers involved. :S
Nooblet94
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barbernator
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barbernator
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Re: HSC 2012 Marathon
use the cos rule for the base triangle with angle 120 degrees. This will give us a relationship between alpha and beta. (the two unknown sides of that base triangle). But we also know that tan of theta and fie (the two angles of the vertical triangles) is 1.8/6.5 and 1.8/9.1 respectively.
We also know that h=(alpha+6.5)tan(theta)=(alpha+6.5)(1.8/6.5) AND h=(beta+9.1)(1.8/9.1) and we can equate these two to find alpha in terms of beta. Now sub this in to the cosine rule equation, and find the positive result for alpha. From this substitute back into the height equation to yield the result. Hey presto, all done.
We can find y. Heres the method for working out. After showing similar triangles and that shit,
use the cos rule for the base triangle with angle 120 degrees. This will give us a relationship between alpha and beta. (the two unknown sides of that base triangle). But we also know that tan of theta and fie (the two angles of the vertical triangles) is 1.8/6.5 and 1.8/9.1 respectively.
We also know that h=(alpha+6.5)tan(theta)=(alpha+6.5)(1.8/6.5) AND h=(beta+9.1)(1.8/9.1) and we can equate these two to find alpha in terms of beta. Now sub this in to the cosine rule equation, and find the positive result for alpha. From this substitute back into the height equation to yield the result. Hey presto, all done.
RishBonjour
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Re: HSC 2012 Marathon
so the answer is 7.3?
thank god, its not 20 or something. (rounded off all my decimals from the equation to find y)
nice work prolet94
so the answer is 7.3?
thank god, its not 20 or something. (rounded off all my decimals from the equation to find y)
nice work prolet94
barbernator
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Re: HSC 2012 Marathon
Two of the roots of the equation x^3 + ax^2 + b = 0 are reciprocals of each other (a and b are real).
i) show that the third root is equal to -b
ii) show that a= b - 1/b
iii) show that the two roots, which are reciprocals, will be real if -0.5 < = b < = 1/2
Two of the roots of the equation x^3 + ax^2 + b = 0 are reciprocals of each other (a and b are real).
i) show that the third root is equal to -b
ii) show that a= b - 1/b
iii) show that the two roots, which are reciprocals, will be real if -0.5 < = b < = 1/2