double exp(double x)

Mathematical Functions: math.h

double atan(double x)

The **return** value is the *inverse tangent*
or *arctangent* of **y/x**.
The **return** value will be expressed in radians
and lie in the interval .

The advantage of **atan2()** over **atan()**
is that, because it is given separate access to the two
original (rectangular) co-ordinates, it is able
to distinguish beween angles in the left and right
half planes (which is not possible if only
**y/x** is passed in, as is the case with **atan()**).

Fri Mar 29 14:35:38 GMT 1996