| InvalidOperationException | x is signaling NaN or ±∞ |
| UnderflowException | result is too small to be represented |
| InexactException | the result is inexact |
| x | cospi(x) |
|---|---|
| NaN | NaN |
| ±∞ | NaN |
| ±0.0 | +1.0 |
| 1/6 | +√3/2 |
| 1/4 | +√2/2 |
| 1/3 | +0.5 |
| 1/2 | +0.0 |
| 2/3 | -0.5 |
| 3/4 | -√2/2 |
| 5/6 | -√3/2 |
| 1.0 | -1.0 |
Returns cosine of xπ.