I hope this is the way you used to do things, but don't do them that way now! Your equation [tex]\sqrt{-1}^2=-1[/tex] is incorrect on at least two counts:

1. [tex]-1^2=-1[/tex], so you're attempting to take the square root of -1. If you meant the square of -1, rather than the negative of 1 squared, put parentheses around -1.
2. [tex]\sqrt{(-1)^2}=+1, not -1[/tex]