#### Previous topic

numpy.sin

#### Next topic

numpy.tan

# numpy.cos

`numpy.``cos`(x[, out]) = <ufunc 'cos'>

  Cosine element-wise.

  Parameters : | x : array_like Input array in radians. out : ndarray, optional Output array of same shape as x.
  Returns : | y : ndarray The corresponding cosine values.
  Raises : | ValueError: invalid return array shape if out is provided and out.shape != x.shape (See Examples)

  Notes

  If out is provided, the function writes the result into it, and returns a reference to out. (See Examples)

  References

  M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions. New York, NY: Dover, 1972.

  Examples

      >>> np.cos(np.array([0, np.pi/2, np.pi]))
      array([  1.00000000e+00,   6.12303177e-17,  -1.00000000e+00])
      >>>
      >>> # Example of providing the optional output parameter
      >>> out2 = np.cos([0.1], out1)
      >>> out2 is out1
      True
      >>>
      >>> # Example of ValueError due to provision of shape mis-matched `out`
      >>> np.cos(np.zeros((3,3)),np.zeros((2,2)))
      Traceback (most recent call last):
        File "<stdin>", line 1, in <module>
      ValueError: invalid return array shape