txheem
Number e (los yog, raws li nws tseem hu ua, tus lej Euler) yog lub hauv paus ntawm lub ntuj logarithm; ib tug lej tsis tu ncua uas yog tus lej irrational.
e = 2.718281828459...
Txoj hauv kev los txiav txim tus lej e (formula):
1. Los ntawm qhov txwv:
Qhov thib ob zoo kawg nkaus txwv:
Lwm txoj kev xaiv (raws li los ntawm De Moivre-Stirling mis):
2. Raws li ib tug series sum:
naj npawb khoom e
1. Kev txwv tsis pub sib yuav e
2. Derivatives
Lub derivative ntawm exponential muaj nuj nqi yog exponential muaj nuj nqi:
(e x)′ = thiabx
Lub derivative ntawm lub ntuj logarithmic muaj nuj nqi yog inverse muaj nuj nqi:
(cave x)′ = (ln x)′ = 1/x
3. Integrals
Lub indefinite integral ntawm ib tug exponential muaj nuj nqi e x yog ib tug exponential muaj nuj nqi e x.
∫ thiabx dx = ex+c
Lub indefinite ib feem ntawm lub ntuj logarithmic muaj nuj nqi cave x:
∫ loge x dx ua = ∫ lnx dx ua = x ln x – x +c
Cov ntsiab lus tseeb ntawm 1 rau e inverse function 1/x yog sib npaug rau 1:
Logarithms nrog puag e
Ntuj logarithm ntawm tus lej x txhais raws li lub hauv paus logarithm x nrog puag e:
ln x = cave x
Exponential Function
Qhov no yog ib tug exponential muaj nuj nqi, uas yog txhais raws li nram no:
f (x) = np(x) = ex
Euler formula
Tus lej nyuaj e iθ sib npaug:
eiθ = cos (θ+ i txhaum (θ)
qhov twg i yog qhov xav txog chav tsev (lub hauv paus square ntawm -1), thiab θ yog tus lej tiag.