Man Scilab

atan
Scilab Function

atan - 2-quadrant and 4-quadrant inverse tangent

Calling Sequence

phi=atan(x)
phi=atan(y,x)

Parameters

Description

The first form computes the 2-quadrant inverse tangent, which is the inverse of tan(phi) . For real x , phi is in the interval (-pi/2, pi/2). For complex x , atan has two singular, branching points +%i , -%i and the chosen branch cuts are the two imaginary half-straight lines [i, i*oo) and (-i*oo, -i].

The second form computes the 4-quadrant arctangent (atan2 in Fortran), this is, it returns the argument (angle) of the complex number x+i*y . The range of atan(y,x) is (-pi, pi].

For real arguments, both forms yield identical values if x>0 .

In case of vector or matrix arguments, the evaluation is done element-wise, so that phi is a vector or matrix of the same size with phi(i,j)=atan(x(i,j)) or phi(i,j)=tan(y(i,j),x(i,j)) .

Examples


// examples with the second form
x=[1,%i,-1,%i]
phasex=atan(imag(x),real(x))
atan(0,-1)
atan(-%eps,-1)

// branch cuts
atan(-%eps + 2*%i)
atan(+%eps + 2*%i)
atan(-%eps - 2*%i)
atan(+%eps - 2*%i)

// values at the branching points
ieee(2)
atan(%i)
atan(-%i)
 
  

See Also

tan ,   ieee ,  

Authors

B.P.
L.V.D. (authors of the complex atan function).

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