sin and cos are slow, is there an alternatve?

My game needs to move by a certain angle. To do this I get the vector of the angle via sin and cos. Unfortunately sin and cos are my bottleneck. I'm sure I do not need this much precision. Is there an alternative to a C sin & cos and look-up table that is decently precise but very fast?

I had found this:

float Skeleton::fastSin( float x )
{
    const float B = 4.0f/pi;
    const float C = -4.0f/(pi*pi);

    float y = B * x + C * x * abs(x);

    const float P = 0.225f;

    return P * (y * abs(y) - y) + y; 
}

Unfortunately, this does not seem to work. I get significantly different behavior when I use this sin rather than C sin.

Thanks