arctangent
The inverse of the tangent function, usually abbreviated arctan. It is defined such that for all real numbers, \(\arctan(x)=a\) if and only if \(\tan(a)=x\). The principal arctangent takes its values in the interval \(\left[-\frac{\pi}{2},\frac{\pi}{2}\right]\).
Arctangent may also be abbreviated by atan or tan
