/*  sdftansr.cpp  by K.Tsuru  */
// function ID 3106     DRADIX
/********************************
SDouble class
It provides the tangent tan x.
Old version's name is "SDouble Tan(const SDouble& x)".
*********************************/
#ifndef SN_H
#include "sn.h"
#endif
SDouble TanRN(const SDouble& x){
    if(x.Sign(3106) == 0) return 0.0;

    int sgn, func = TAN_CALC;
    SDouble s, c, r;
    sgn = GetTriCalcMethod(x, r, &func);    // |r| < pi/4
//When tan(x) has an infinite value the domain error will occur in GetTriCalcMethod(x,r,&func);
    if(sgn == 0) return 0.0;

// tan(r) = sin(r)/cos(r)
    if(r.NetRdxExp() < -1){ // |x| < 1/DRADIX^2
        s = SinSeries(r);
        c = CosRN(r);
    } else{
        RealSize C;
        uint up = s.ProperUpPrec(2u);
        if(up) C.SetEffFig(x.EffFig() + up, C.TEMP_EXTEND);
        s = SinRN(r);       // |r| < pi/4 , |s| < sqrt(0.5)
        c = Sqrt(1.0-s*s);
        if(up) C.SetEffFig(0);
    }

    if(func == TAN_CALC) r = s*DReciprocal(c);
    else                 r = c*DReciprocal(s);  // cot x
    if(sgn < 0) r.ChangeSign();     // r = -r;
    return r;
}