We factor to determine the square factors. The rule which preserves the principal value of a radical expression is only positive numbers can come out from under a radical sign. When just the square root of negative one is left, we write that as i.
[tex] \sqrt{-90} = \sqrt{-1 \times 2 \times 3^2 \times 5} = 3 \sqrt{-10} = 3 \sqrt{10} \ i[/tex]
sqrt -90 = sqrt90 * i
you can write it as √90i or 9.49i to nearest hundredth
