FOGD includes an implementation of sine and cosine calculations using a method that's described in this blog post. The way it's implemented in FOGD, it seems like p1 is meant to represent the cosine and p2 the sine; however, looking at the formulas from the post (and computing the values on my own), this appears to be flipped, i.e. p1 is sine and p2 is cosine. This leads to a problem here where the sign of p2 is flipped if the angle of negative. This would be correct if p2 was sine, but is not correct since p2 is actually the cosine of the angle.
FOGD includes an implementation of sine and cosine calculations using a method that's described in this blog post. The way it's implemented in FOGD, it seems like p1 is meant to represent the cosine and p2 the sine; however, looking at the formulas from the post (and computing the values on my own), this appears to be flipped, i.e. p1 is sine and p2 is cosine. This leads to a problem here where the sign of p2 is flipped if the angle of negative. This would be correct if p2 was sine, but is not correct since p2 is actually the cosine of the angle.