Math Problem of the Day

I will post a challenging math problem each day. The level of difficulty will vary, but most problems should not require any specialized knowledge beyond calculus. Problems are also posted on Twitter using the hashtag #mathpotd.

Thursday, May 6, 2010

1, 101, 10101, 1010101, ...

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Show that, in the sequence 1, 101, 10101, 1010101, ... only the number 101 is prime.
1 comment:
Friday, October 23, 2009

Arctangent sum

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Evaluate the sum of arctan(1/(2n^2)) from n=1 to infinity.
Thursday, October 22, 2009

Line joining tangent circles

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A circle of radius 4 is tangent to a circle of radius 9, and a line is tangent to both circles at A and B. Find |AB|.
Wednesday, October 21, 2009

x^y = y^x

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If 0
Tuesday, October 20, 2009

3D Tic-Tac-Toe

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In how many ways can you get three in a row in three-dimensional tic-tac-toe (noughts and crosses)?
Monday, October 19, 2009

Colorado balloon incident

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I gave my students an assignment related to the Colorado balloon incident. Any comments or suggestions would be appreciated. Are there other...

f(f(x)) = x^2

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Find a real function f so that f(f(x)) = x^2 for all x.
1 comment:
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