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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
commit | 116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch) | |
tree | 8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/math.rst | |
parent | 739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff) | |
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diff --git a/Doc/library/math.rst b/Doc/library/math.rst new file mode 100644 index 0000000..17c75d3 --- /dev/null +++ b/Doc/library/math.rst @@ -0,0 +1,227 @@ + +:mod:`math` --- Mathematical functions +====================================== + +.. module:: math + :synopsis: Mathematical functions (sin() etc.). + + +This module is always available. It provides access to the mathematical +functions defined by the C standard. + +These functions cannot be used with complex numbers; use the functions of the +same name from the :mod:`cmath` module if you require support for complex +numbers. The distinction between functions which support complex numbers and +those which don't is made since most users do not want to learn quite as much +mathematics as required to understand complex numbers. Receiving an exception +instead of a complex result allows earlier detection of the unexpected complex +number used as a parameter, so that the programmer can determine how and why it +was generated in the first place. + +The following functions are provided by this module. Except when explicitly +noted otherwise, all return values are floats. + +Number-theoretic and representation functions: + + +.. function:: ceil(x) + + Return the ceiling of *x* as a float, the smallest integer value greater than or + equal to *x*. + + +.. function:: fabs(x) + + Return the absolute value of *x*. + + +.. function:: floor(x) + + Return the floor of *x* as a float, the largest integer value less than or equal + to *x*. + + +.. function:: fmod(x, y) + + Return ``fmod(x, y)``, as defined by the platform C library. Note that the + Python expression ``x % y`` may not return the same result. The intent of the C + standard is that ``fmod(x, y)`` be exactly (mathematically; to infinite + precision) equal to ``x - n*y`` for some integer *n* such that the result has + the same sign as *x* and magnitude less than ``abs(y)``. Python's ``x % y`` + returns a result with the sign of *y* instead, and may not be exactly computable + for float arguments. For example, ``fmod(-1e-100, 1e100)`` is ``-1e-100``, but + the result of Python's ``-1e-100 % 1e100`` is ``1e100-1e-100``, which cannot be + represented exactly as a float, and rounds to the surprising ``1e100``. For + this reason, function :func:`fmod` is generally preferred when working with + floats, while Python's ``x % y`` is preferred when working with integers. + + +.. function:: frexp(x) + + Return the mantissa and exponent of *x* as the pair ``(m, e)``. *m* is a float + and *e* is an integer such that ``x == m * 2**e`` exactly. If *x* is zero, + returns ``(0.0, 0)``, otherwise ``0.5 <= abs(m) < 1``. This is used to "pick + apart" the internal representation of a float in a portable way. + + +.. function:: ldexp(x, i) + + Return ``x * (2**i)``. This is essentially the inverse of function + :func:`frexp`. + + +.. function:: modf(x) + + Return the fractional and integer parts of *x*. Both results carry the sign of + *x*, and both are floats. + +Note that :func:`frexp` and :func:`modf` have a different call/return pattern +than their C equivalents: they take a single argument and return a pair of +values, rather than returning their second return value through an 'output +parameter' (there is no such thing in Python). + +For the :func:`ceil`, :func:`floor`, and :func:`modf` functions, note that *all* +floating-point numbers of sufficiently large magnitude are exact integers. +Python floats typically carry no more than 53 bits of precision (the same as the +platform C double type), in which case any float *x* with ``abs(x) >= 2**52`` +necessarily has no fractional bits. + +Power and logarithmic functions: + + +.. function:: exp(x) + + Return ``e**x``. + + +.. function:: log(x[, base]) + + Return the logarithm of *x* to the given *base*. If the *base* is not specified, + return the natural logarithm of *x* (that is, the logarithm to base *e*). + + .. versionchanged:: 2.3 + *base* argument added. + + +.. function:: log10(x) + + Return the base-10 logarithm of *x*. + + +.. function:: pow(x, y) + + Return ``x**y``. + + +.. function:: sqrt(x) + + Return the square root of *x*. + +Trigonometric functions: + + +.. function:: acos(x) + + Return the arc cosine of *x*, in radians. + + +.. function:: asin(x) + + Return the arc sine of *x*, in radians. + + +.. function:: atan(x) + + Return the arc tangent of *x*, in radians. + + +.. function:: atan2(y, x) + + Return ``atan(y / x)``, in radians. The result is between ``-pi`` and ``pi``. + The vector in the plane from the origin to point ``(x, y)`` makes this angle + with the positive X axis. The point of :func:`atan2` is that the signs of both + inputs are known to it, so it can compute the correct quadrant for the angle. + For example, ``atan(1``) and ``atan2(1, 1)`` are both ``pi/4``, but ``atan2(-1, + -1)`` is ``-3*pi/4``. + + +.. function:: cos(x) + + Return the cosine of *x* radians. + + +.. function:: hypot(x, y) + + Return the Euclidean norm, ``sqrt(x*x + y*y)``. This is the length of the vector + from the origin to point ``(x, y)``. + + +.. function:: sin(x) + + Return the sine of *x* radians. + + +.. function:: tan(x) + + Return the tangent of *x* radians. + +Angular conversion: + + +.. function:: degrees(x) + + Converts angle *x* from radians to degrees. + + +.. function:: radians(x) + + Converts angle *x* from degrees to radians. + +Hyperbolic functions: + + +.. function:: cosh(x) + + Return the hyperbolic cosine of *x*. + + +.. function:: sinh(x) + + Return the hyperbolic sine of *x*. + + +.. function:: tanh(x) + + Return the hyperbolic tangent of *x*. + +The module also defines two mathematical constants: + + +.. data:: pi + + The mathematical constant *pi*. + + +.. data:: e + + The mathematical constant *e*. + +.. note:: + + The :mod:`math` module consists mostly of thin wrappers around the platform C + math library functions. Behavior in exceptional cases is loosely specified + by the C standards, and Python inherits much of its math-function + error-reporting behavior from the platform C implementation. As a result, + the specific exceptions raised in error cases (and even whether some + arguments are considered to be exceptional at all) are not defined in any + useful cross-platform or cross-release way. For example, whether + ``math.log(0)`` returns ``-Inf`` or raises :exc:`ValueError` or + :exc:`OverflowError` isn't defined, and in cases where ``math.log(0)`` raises + :exc:`OverflowError`, ``math.log(0L)`` may raise :exc:`ValueError` instead. + + +.. seealso:: + + Module :mod:`cmath` + Complex number versions of many of these functions. + |