Sunday, November 21, 2010

The story of enigmatic e

Okay, what is e in the first place? It the one of the few mathematical constant you might ever encounter. e is an irrational number, and it can't be rerepresented as a fraction. The value of e is 2.7182 8182 8459 0452 3536 0287 4713 5266 2497 7572…. Where … is a non repeating sequence. Where does this enigmatic number came from?

It turns out that it begins with money. Yes, I'm not kidding. In 17th century, Jacob Bernoulli was studying an interesting problem about compound interest. What is the problem you may ask. Well, here it is.
Let's say that a bank give you 100% interest per year (no bank will give you that much ) and you put $1.00 in your account. At the end of the year the money in your acount will be $2.00. But what if there is another bank that give 50% interest per half a year? At the end of the year your saving will be $2.25 if you put your money there. What about 33.3…% per 4 months? Your saving will be $2.37 at the end of the year. You obviously want the one that give the highest interest right? If there is another bank that offer higher frequency of interest computation, we will jump over it don't we (assuming the number of computation of interest times percentage of interest is the same)? This leads us to infinite division of interest.

So, what is the formula? It is basically f(n) = (1+1/n)^n. Where n is the number of division (assuming that the the number of computation of interest times percentage of interest is 100%. If it's not, then you need to do some manipulation).

What e has to do with this? Before I answer the question, try playing with the formula a little bit. You might notice something interesting. As you increase the value of n, the difference between f(n) and f(n-1) become smaller and smaller. It tells you that there is a limit to the value of f(n) as n approaches infinity. And what it is? It's the famous e!

-Mit freundlichem Gruss und, Heil Schrödingers Katze!

Saturday, September 4, 2010

Riemannian Geometry

Okay, let's start from what is Riemannian Geometry. It is simply Geometry on curved plane or what commonly called eliptical geometry.

Just look at the picture. In the positive curvature, the sum of the angles is > 180 degree or where is the Goddamn pi π and it is smaller when it is in saddle shaped curvature.

Need a better picture? I'll get them later.

Tuesday, June 22, 2010

Do you know that.....

Do you know that in Riemann Geometry, sum of the angles of a triangle is not always 180°?

Explanation will come later.

Sunday, May 30, 2010

Project Euler

Quite recently, I stumbled upon this so called Project Euler, named after famed German Mathematician. It is a collection of challenging mathematical questions.
Here is the description from the website:

Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.

The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.

Good luck in trying some of the questions XD

Sunday, May 23, 2010

Surprising Number Pattern

1 x 8 + 1 =9
12 x 8 + 2 = 98
123 x 8 + 3 = 987
1234 x 8 + 4 = 9876
12345 x 8 + 5 = 98765
123456 x 8 + 6 = 987654
1234567 x 8 + 7 = 9876543
12345678 x 8 + 8 = 98765432
123456789 x 8 + 9 = 987654321

edit : taken from the book Math Wonders to Inspire Teachers and Students.

Friday, May 21, 2010

Interesting Pattern

Have you ever noticed this?

11^2 = 121
111^2 = 12321
1111^2 = 1234321
11111^2 = 123454321
...
111111111^2 = 12345678987654321
1111111111^2 = 1234567900987654321
and so on.

edit : taken from the book Math Wonders to Inspire Teachers and Students.

Monday, May 17, 2010

How true is this?

When I was bored enough during maths lesson, I jotted down some prime number and find something rather surprising. Prime number that is larger or equal to 7 can be re-represented as the sum of three prime numbers. in short, d = a+b+c where a,b,c and d are prime number and d≥7.

Some example up to prime number that is less than 100 would be :
7=2+2+3
11=2+2+7
13=3+3+7
17=5+5+7
19=7+7+5
23=11+5+7
29=23+3+3
31=23+3+5
37=31+3+3
41=31+5+5
43=31+5+7
47=37+5+5
53=43+5+5
59=53+3+3
61=31+13+17
67=61+3+3
71=61+5+5
73=67+3+3
79=73+3+3
83=73+5+5
89=79+5+5
97=41+37+19

Enough of spamming out of the blue.

Thanks to Mr Chew for correcting the mistake.

L'Hospital Rule Calculator