scipy.special.cosm1#

scipy.special.cosm1(x, out=None) = <ufunc 'cosm1'>#

cos(x) - 1 for use when x is near zero.

Parameters:

xarray_like: Real valued argument.
outndarray, optional: Optional output array for the function results.

Returns:

scalar or ndarray: Values of cos(x) - 1.

See also

expm1, log1p

Notes

cosm1 has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable SCIPY_ARRAY_API=1 and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

Library	CPU	GPU
NumPy	✅	n/a
CuPy	n/a	✅
PyTorch	✅	⛔
JAX	⚠️ no JIT	⛔
Dask	✅	n/a

See Support for the array API standard for more information.

Examples

>>> import numpy as np
>>> import scipy.special as sc

It is more accurate than computing cos(x) - 1 directly for x around 0.

>>> x = 1e-30
>>> np.cos(x) - 1
0.0
>>> sc.cosm1(x)
-5.0000000000000005e-61