Advanced Graphing error?

[lrdheat]

My Prime and CASIO fx-CG10 both show (-1.05)^(498/1001)=-1.02457..., and show the same if I take -1.05^498, and then take 1001root of that answer. What is really odd to me is that 498 is even, and should produce the answer that you are reporting!

Is this a bug, or am I missing something, and both the positive and negative answers are correct, yielding both values when taking the sin (the double plot for X<0)?