The tan function returns the tangent of angle which is in radians.
In complex expressions, angle is complex, and tan(angle) returns a complex value:
tan(x+iy)=cos(x+iy)sin(x+iy)=cos(2x)+cosh(2y)sin(2x)+isinh(2y).
See Also
atan, atan2, sin, cos, sec, csc, cot