e

e is a mathematical constant. A mathematical constant is any well-defined real number that is significantly interesting in some way. e has a value of about 2.718. e is an irrational number. It is named after Leonhard Euler and can also be called Euler's number because Euler proved e is an irrational number.
You can calculate e with this formula: 1 + 1/1! +1/2! +1/3! +1/4! +1/5! + 1/6! + 1/7! and so on so forth. if calculated out, the first few terms are 1 + 1 + 1/2 + 1/6 + 1/24 + 1/120 = 2.718055556. 
e is found in many interesting areas. To memorize e, remember this sentence:
to express e remember to memorize a sentence to simplify this.
(count the letters).
The value of e is used to find a nonlinear increase or decrease. e occurs naturally with some frequency so it is the base of natural logarithms.

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next time: logarithms

Pythagoras

Kazuma has already done a post about the Pythagorean Theorem. Who was behind this equation?
Why, Pythagoras, of course.
Pythagoras is recognized as the first mathematician. It was probably Pythagoras who said that numbers can uncover the secrets of the universe.
Pythagoras is known the best for his Pythagorean Theorem where  .
This formula is used to find the approximate length of the hypotenuse of a right triangle. Note, this only works on right triangles.
Pythagoras paved the paths for all aspiring mathematicians.

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