cos¶
- cos(x: array, /) array ¶
Calculates an implementation-dependent approximation to the cosine for each element
x_i
of the input arrayx
.Each element
x_i
is assumed to be expressed in radians.Note
The cosine is an entire function on the complex plane and has no branch cuts.
Note
For complex arguments, the mathematical definition of cosine is
\[\begin{split}\begin{align} \operatorname{cos}(x) &= \sum_{n=0}^\infty \frac{(-1)^n}{(2n)!} x^{2n} \\ &= \frac{e^{jx} + e^{-jx}}{2} \\ &= \operatorname{cosh}(jx) \end{align}\end{split}\]where \(\operatorname{cosh}\) is the hyperbolic cosine.
- Parameters:
x (array) – input array whose elements are each expressed in radians. Should have a floating-point data type.
- Returns:
out (array) – an array containing the cosine of each element in
x
. The returned array must have a floating-point data type determined by Type Promotion Rules.
Notes
Special cases
For real-valued floating-point operands,
If
x_i
isNaN
, the result isNaN
.If
x_i
is+0
, the result is1
.If
x_i
is-0
, the result is1
.If
x_i
is+infinity
, the result isNaN
.If
x_i
is-infinity
, the result isNaN
.
For complex floating-point operands, special cases must be handled as if the operation is implemented as
cosh(x*1j)
.Changed in version 2022.12: Added complex data type support.