Dan Meyer: Math class needs a makeover. Weierstrass functions. Weierstrass functions are famous for being continuous everywhere, but differentiable "nowhere".
Here is an example of one: It is not hard to show that this series converges for all x. In fact, it is absolutely convergent. It is also an example of a fourier series, a very important and fun type of series. It can be shown that the function is continuous everywhere, yet is differentiable at no values of x. Here's a graph of the function.
You can see it's pretty bumpy. Below is an animation, zooming into the graph at x=1. Wikipedia and MathWorld both have informative entries on Weierstrass functions. Nerd Paradise : Divisibility Rules for Arbitrary Divisors. It's rather obvious when a number is divisible by 2 or 5, and some of you probably know how to tell if a number is divisible by 3, but it is possible to figure out the division 'rule' for any number.
Here are the rules for 2 through 11... The last digit is divisible by 2. The sum of all the digits in the number is divisible by 3. The last 2 digits are divisible by 4. The last digit is 5 or 0. The number is both divisible by 2 and divisible by 3. Cut the number into 2 parts: the last digit and everything else before that. The last 3 digits are divisible by 8 The sum of all the digits in the number is divisible by 9. The last digit is a 0. Break the number into two parts (like you did for the division by 7 rule). Also there is a quick way for determining divisibility by 11 for 3-digit numbers: If the inner digit is larger than the two outer digits, then it is divisible by 11 if the inner digit is the sum of the two outer digits.
Rules for all divisors ending in 1... User Comments: 9. Math doesn't suck, you do. Every time I hear someone say "I suck at math," I immediately think he or she is a moron. If you suck at math, what you really suck at is following instructions. This shirt is birth control. Sucking at math is like sucking at cooking. I'm tired of eating shitty food because you're too much of a dipshit to follow a recipe.
Also, I'm tired of hearing people brag about how they can't cook like it's some kind of badge of honor. Math is exactly like cooking: just follow the recipe. Math isn't some voodoo that only smart people understand. Theoretical math is cool as shit. Ever heard of Pascal's triangle? No, because you're too busy saying the same tired excuse every other dickhead spews out about math: "when will I ever use this in life? " First of all, if you're leading your life in such a way that you never have to do math, congratulations, you are a donkey. Why is math the only discipline that has to put up with this bullshit?
People didn't invent this stuff because they were bored. PatrickJMT.