# atan2

Returns the angle `theta`

of the polar coordinates `(r, theta)`

that correspond
to the rectangular coordinates `(x, y)`

by computing the arc tangent of the value y / x;
the returned value is an angle in the range from `-PI`

to `PI`

radians.

Special cases:

`atan2(0.0, 0.0)`

is`0.0`

`atan2(0.0, x)`

is`0.0`

for`x > 0`

and`PI`

for`x < 0`

`atan2(-0.0, x)`

is`-0.0`

for 'x > 0`and`

-PI`for`

x < 0``atan2(y, +Inf)`

is`0.0`

for`0 < y < +Inf`

and`-0.0`

for '-Inf < y < 0``atan2(y, -Inf)`

is`PI`

for`0 < y < +Inf`

and`-PI`

for`-Inf < y < 0`

`atan2(y, 0.0)`

is`PI/2`

for`y > 0`

and`-PI/2`

for`y < 0`

`atan2(+Inf, x)`

is`PI/2`

for finite`x`

y`atan2(-Inf, x)`

is`-PI/2`

for finite`x`

`atan2(NaN, x)`

and`atan2(y, NaN)`

is`NaN`