demonstration

Projective Planes

Most of you know how to make a Mobius band—take a strip of paper and glue the ends with a half-twist. This object now has the property that is has only one “side”. It also has only one edge. Well, a disc has only one...

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Birthday Problem

How many people do you need in a group to ensure at least a 50 percent probability that 2 people in the group share a birthday? Let’s take a show of hands. How many people think 30 people is enough? 60? 90? 180? 360? Surprisingly,...

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Suspended Rope Trick

What is the shape of a suspended rope? Is there some function that describes it? Answer: it’s the cosh curve! Presentation Suggestions:This may be seen quite dramatically by putting up a transparency of the catenary y = cosh x and suspending a rope in front of...

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