/// <summary>
/// Calculates tan(x)
/// </summary>
public void Tan()
{
if (IsSpecialValue)
{
//Tan(x) has no limit as x->inf
if (SpecialValue == SpecialValueType.INF_MINUS || SpecialValue == SpecialValueType.INF_PLUS)
{
SetNaN();
}
else if (SpecialValue == SpecialValueType.ZERO)
{
SetZero();
}
return;
}
if (pi == null || pi.mantissa.Precision.NumBits != mantissa.Precision.NumBits)
{
CalculatePi(mantissa.Precision.NumBits);
}
//Work out the sign change (involves replicating some rescaling).
bool sign = mantissa.Sign;
mantissa.Sign = false;
if (mantissa.IsZero())
{
return;
}
//Rescale into 0 <= x < pi
if (GreaterThan(pi))
{
//There will be an inherent loss of precision doing this.
BigFloat newAngle = new BigFloat(this);
newAngle.Mul(piRecip);
newAngle.FPart();
newAngle.Mul(pi);
Assign(newAngle);
}
//Rescale to -pi/2 <= x < pi/2
if (!LessThan(piBy2))
{
Sub(pi);
}
//Now the sign of the sin determines the sign of the tan.
//tan(x) = sin(x) / sqrt(1 - sin^2(x))
Sin();
BigFloat denom = new BigFloat(this);
denom.Mul(this);
denom.Sub(new BigFloat(1, mantissa.Precision));
denom.mantissa.Sign = !denom.mantissa.Sign;
if (denom.mantissa.Sign)
{
denom.SetZero();
}
denom.Sqrt();
Div(denom);
if (sign) mantissa.Sign = !mantissa.Sign;
}