Developpez.com

Python

Choisissez la catégorie, puis la rubrique :

6.2 cmath -- Mathematical functions for complex numbers

6.2 cmath -- Mathematical functions for complex numbers

This module is always available. It provides access to mathematical functions for complex numbers. The functions are:

acos( x)
Return the arc cosine of x. There are two branch cuts: One extends right from 1 along the real axis to ∞, continuous from below. The other extends left from -1 along the real axis to -∞, continuous from above.

acosh( x)
Return the hyperbolic arc cosine of x. There is one branch cut, extending left from 1 along the real axis to -∞, continuous from above.

asin( x)
Return the arc sine of x. This has the same branch cuts as acos().

asinh( x)
Return the hyperbolic arc sine of x. There are two branch cuts, extending left from ±1j to ±-∞j, both continuous from above. These branch cuts should be considered a bug to be corrected in a future release. The correct branch cuts should extend along the imaginary axis, one from 1j up to ∞j and continuous from the right, and one from -1j down to -∞j and continuous from the left.

atan( x)
Return the arc tangent of x. There are two branch cuts: One extends from 1j along the imaginary axis to ∞j, continuous from the left. The other extends from -1j along the imaginary axis to -∞j, continuous from the left. (This should probably be changed so the upper cut becomes continuous from the other side.)

atanh( x)
Return the hyperbolic arc tangent of x. There are two branch cuts: One extends from 1 along the real axis to ∞, continuous from above. The other extends from -1 along the real axis to -∞, continuous from above. (This should probably be changed so the right cut becomes continuous from the other side.)

cos( x)
Return the cosine of x.

cosh( x)
Return the hyperbolic cosine of x.

exp( x)
Return the exponential value e**x.

log( x[, base])
Returns the logarithm of x to the given base. If the base is not specified, returns the natural logarithm of x. There is one branch cut, from 0 along the negative real axis to -∞, continuous from above. Changed in version 2.4: base argument added.

log10( x)
Return the base-10 logarithm of x. This has the same branch cut as log().

sin( x)
Return the sine of x.

sinh( x)
Return the hyperbolic sine of x.

sqrt( x)
Return the square root of x. This has the same branch cut as log().

tan( x)
Return the tangent of x.

tanh( x)
Return the hyperbolic tangent of x.

The module also defines two mathematical constants:

pi
The mathematical constant pi, as a real.

e
The mathematical constant e, as a real.

Note that the selection of functions is similar, but not identical, to that in module math. The reason for having two modules is that some users aren't interested in complex numbers, and perhaps don't even know what they are. They would rather have math.sqrt(-1) raise an exception than return a complex number. Also note that the functions defined in cmath always return a complex number, even if the answer can be expressed as a real number (in which case the complex number has an imaginary part of zero).

A note on branch cuts: They are curves along which the given function fails to be continuous. They are a necessary feature of many complex functions. It is assumed that if you need to compute with complex functions, you will understand about branch cuts. Consult almost any (not too elementary) book on complex variables for enlightenment. For information of the proper choice of branch cuts for numerical purposes, a good reference should be the following:

See Also:

Kahan, W: Branch cuts for complex elementary functions; or, Much ado about nothing's sign bit. In Iserles, A., and Powell, M. (eds.), The state of the art in numerical analysis. Clarendon Press (1987) pp165-211.

See About this document... for information on suggesting changes.
Quels sont les frameworks que vous aimeriez apprendre en 2019 ?
Éducation : Python deviendra le langage officiel de programmation en France, dans le cadre de la réforme du Bac et du lycée
Quel langage de programmation comporte le plus de vulnérabilités en matière de sécurité ?
Introduction à la bibliothèque Pandas - Analyse de données en Python, un tutoriel de Gabor Laszlo Hajba traduit par l'équipe de rédaction
Contacter le responsable de la rubrique Python

Partenaire : Hébergement Web