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'''''e''''' is a useful [[mathematical]] constant which is a [[transcendental]] number approximately equal to 2.718281828459045 . ''e'' can be used in [[logarithm]]s as the base, called a [[natural logarithm]]. ''e'' is named for [[Swiss]] [[mathematician]] [[Leonhard Euler]], though he did not discover the constant.

'''''e''''' is a useful [[mathematical]] constant which is a [[transcendental]] number approximately equal to 2.718281828459045 . ''e'' can be used in [[logarithm]]s as the base, called a [[natural logarithm]]. ''e'' is named for [[Swiss]] [[mathematician]] [[Leonhard Euler]], though he did not discover the constant.

It has some remarkable properties that its [[exponential]] to any [[real number]] <math>x</math> is:

It has some remarkable properties: For example:

:<math>\frac{d}{dx}e^x = e^x.</math>

:<math>\frac{d}{dx}e^x = e^x.</math>

The exponetial function is the [[eigenfunction]] of the [[derivative]] operator.

(i.e. the exponetial function is an [[eigenfunction]] of the [[derivative]] operator, with [[eigenvalue]] 1).

==Formulae for ''e''==

==Formulae for ''e''==