Countolaf
Level 11 poster
Count Omar, the Wild Warrior
Posts: 1,113
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Post by Countolaf on Jan 7, 2006 19:11:28 GMT 1
Some problems I found on a site:
Two perfect logicians, S and P, are told that integers x and y have been chosen such that 1 < x < y and x+y < 100. S is given the value x+y and P is given the value xy. They then have the following conversation.
P: I cannot determine the two numbers. S: I knew that. P: Now I can determine them. S: So can I.
Given that the above statements are true, what are the two numbers?
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Roll a standard pair of six-sided dice, and note the sum. There is one way of obtaining a 2, two ways of obtaining a 3, and so on, up to one way of obtaining a 12. Find all other pairs of six-sided dice such that:
1. The set of dots on each die is not the standard {1,2,3,4,5,6}. 2. Each face has at least one dot. 3. The number of ways of obtaining each sum is the same as for the standard dice.
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Find all integer solutions of y² = x³ - 432
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Let x, y, n be positive integers, with n > 1. How many solutions are there to the equation x^n - y^n = 2100?
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Countolaf
Level 11 poster
Count Omar, the Wild Warrior
Posts: 1,113
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Post by Countolaf on Jan 8, 2006 22:29:16 GMT 1
Another problem: Find the value of x in the equation: [cos(x)][cos(5x)][cos(7x)] = tan30° By the way, 3 of the 4 problems I put before I can't solve myself
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Post by Fox Mc Cloud on Jan 8, 2006 22:54:29 GMT 1
Which one can you solve?
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Countolaf
Level 11 poster
Count Omar, the Wild Warrior
Posts: 1,113
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Post by Countolaf on Jan 8, 2006 23:27:51 GMT 1
"Find the value of x in the equation:
[cos(x)][cos(5x)][cos(7x)] = tan30°"
And
"Two perfect logicians, S and P, are told that integers x and y have been chosen such that 1 < x < y and x+y < 100. S is given the value x+y and P is given the value xy. They then have the following conversation.
P: I cannot determine the two numbers. S: I knew that. P: Now I can determine them. S: So can I.
Given that the above statements are true, what are the two numbers?"
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Post by Fox Mc Cloud on Jan 9, 2006 11:47:54 GMT 1
Another problem: Find the value of x in the equation: [cos(x)][cos(5x)][cos(7x)] = tan30° cos(x)*cos(5x)*cos(7x)=tan30° <-> cos(x+5x+7x)=tan30° <-> cos(13x)=tan30° <-> 13x=cos -1(tan30°) <-> x={cos -1(tan30°)}/13 <-> x=4.21 Correct?
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Countolaf
Level 11 poster
Count Omar, the Wild Warrior
Posts: 1,113
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Post by Countolaf on Jan 9, 2006 22:08:15 GMT 1
I checked my solution of that thing and I noticied I done a thing wrong, so I haven't done it correctly yet Your solution is wrong, Fox cos(x)*cos(5x)*cos(7x) is not equal to cos(x+5x+7x)
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Post by Fox Mc Cloud on Jan 9, 2006 22:27:12 GMT 1
Is it equal to cos(x*5x*7x)?
Btw solve my things in the thread I made.
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Countolaf
Level 11 poster
Count Omar, the Wild Warrior
Posts: 1,113
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Post by Countolaf on Jan 10, 2006 17:53:57 GMT 1
The only things you can do is turning products in sums and sums in products. cosacosb = [cos(a+b) + cos(a-b)]/2 cosx + cosy = 2cos[(x+y)/2]cos[(x-y)/2]
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Post by Fox Mc Cloud on Jan 10, 2006 18:19:19 GMT 1
Hummmmmm
I'll try this again later.
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