# Is the sqrt( -1) = i , or plus-minus i

1. Nov 1, 2008

### Unassuming

When I am solving an equation and I take the sqrt of both sides, one of which is -1.

Do I put i, or plusminus i ?

2. Nov 1, 2008

### gabbagabbahey

It's just $i$ (although engineers use $j$ just to be obstinate)

3. Nov 1, 2008

### mgb_phys

sqrt(-1) is i but the solution to x2 = 1 is +1 /-1