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Two Problems |
2004-07-12 |
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Justina pose la question :
i cant figure out the range of this equation in interval form because the highest point seems to be a decimal. please help f(x) = x + sqrt(4-x2)
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Building Design A circular air duct of diameter D is fit firmly into the right-angle corner where a basement wall meets the floor (see figure). Find the diameter of the largest water pipe that can be run in the right-angle corner behind the air duct.
Claude Tardif and Penny Nom lui répond. |
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The tangent of theta |
2004-07-10 |
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Jacob pose la question :
P is a point on a unit circle with coordinates(0.6,0.8). Find tan of theta. My book shows me how to do it,"tan of theta=opp./adj.=0.8/0.6=4/3,"and leaves it as that's the answer(4/3).When do we know from a problem to find the angle measure (in this case, the angle measure of theta) and how do we know when to give something like 4/3 without converting it to the angle measure?
Penny Nom lui répond. |
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Four digits |
2004-07-10 |
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Rob pose la question :
I am always interested to know how the for digit works. I mean, you have correctly put it that the total numbers obtain from 0000 thru 9999 are 10,000. My question is, is there any simple formula to turn this simple 4 figures of say: 1234.
Penny Nom lui répond. |
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The circle through three points |
2004-07-06 |
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Jim pose la question :
I am a student trying to solve math problem. I'd like to calculate the radius of the circle that exactly fits any three points. If the points are (X1,Y1), (X2,Y2), and (X3,Y3), what is the radius of the circle that contains those three points?
Penny Nom lui répond. |
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Vectors |
2004-07-06 |
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Annie pose la question :
a=3i-j+2k and b=i+3j-2k, determine the magnitude and direction cosines of the product vector and show that it is perpendicular to a vector c=9i+2j+2k.
Chris Fisher lui répond. |
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An ineqlality with absolute values |
2004-07-05 |
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Uneeza pose la question :
abs(x2 - 4x) > 3
Claude Tardif lui répond. |
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Factoring integers |
2004-07-02 |
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A student pose la question :
After looking at all the info I could get about NFS, I still have some questions that are unsolved:
First of all: If someone found an algorithm that has a worst case running time of N*Log(N) to factor an integer n into his divisors, would it be quicker or slower then the number field sieve algorithm?
secondly, what exactly is the time complexity of the Number Field Sieve algorithm, if I would factor an integer n?
Claude Tardif lui répond. |
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Choosing 5 numbers from 1,...,36 |
2004-06-30 |
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A lottery player? pose la question :
how many combinations are there for the numbers 1thru 36 when only using each number once in groups of five
Penny Nom lui répond. |
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Simplify |
2004-06-27 |
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Tiff pose la question :
Simplify:
-3x (x2 + 2)
(x + 2) (x + 3)
Penny Nom lui répond. |
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Aunt Lucy's letter |
2004-06-27 |
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Olivia pose la question :
"Dear bob,
now that i am getting on (70 today). i want to give you some of my money, i shall give you a sum each year, starting now. you can choose which of the following schemes you would like me to use.
a) £100 now, £90 next year,£80 the yaer after and so on.
b) £10 now, £20 next year, £ 30 the next year and so on.
c) £10 now, 1.5 times as much next year, 1.5 times as much the year after that and so on.
d)£1 now, £2 next year, £ 4 the year after, £8 the year after and so on.
of course these schemes will only operate while i am alive. i look forward to hearing which scheme you choose and why!
Best wishes,
Aunt Lucy."
Penny Nom and Claude Tardif lui répond. |
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Undercapatalized small businesses |
2004-06-26 |
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Greg pose la question :
Suppose that 30% of all small businesses are undercapitalized. 40% of all
undercapitalized small businesses fail and 20% of all small businesses that
are not undercapitalized fail. A small business is chosen at random. The
probability that the small business succeeds if it is undercapitalized is? Greg
Penny Nom lui répond. |
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Pick a number greater than 1 |
2004-06-25 |
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A student pose la question :
I understand that when you pick a number greater than 1 and less than 10; multiply it by 7 and add 23, then add the digits of that number until you get a one digit number. Then multiply that number by 9, add the digits of that number until you get a one digit number, subtract 3 from that number and divide the difference by 3; that this process will always give you the result of 2. Does this have a name or theory for it as to why the answer will always be 2?
Penny Nom lui répond. |
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(a+b) + 5i = 9 + ai |
2004-06-25 |
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Josh pose la question :
The question which someone gave you (a+b) + 5i = 9 + ai question) gave me trouble.
Penny Nom lui répond. |
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(ln(50/x)) / (ln(40/x)) = a |
2004-06-21 |
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Un eleve pose la question :
(ln(50/x)) / (ln(40/x)) = a = constante
comment extraire la variable x ???
Claude Tardif lui répond. |
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How much loam to fill a hole? |
2004-06-19 |
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Harry pose la question :
Can you tell me how much loam I would need to fill a hole 15 feet in dia. x 6 inches deep.
Penny Nom lui répond. |
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