ATAN2

Syntax: | `vout = ATAN2( v1, v2 )`

The `ATAN2(v1,v2)` function returns the Arc Tangent of `v1/v2`, with -π `< ATAN2(v1,v2) ≤` π.

- If `v1 > 0`, the result is positive.
- If `v1 = 0`, the result is zero if `v2 > 0` and π if `v2 < 0`.
- If `v1 < 0`, the result is negative. If the value of the second argument is zero, the absolute value of the result is π`/2`.

Both arguments must not have the value zero.