You'll have to forgive me, I'm not sure of the tag for square roots (if there is a link to all math signs, could you please link it?)
You should know that the argument of z = a + ib is where you have to be careful what quadrant (and hence value) you choose for ..... A simple argand diagram showing z = a + ib will help you make that decision.
For the question you've posted, .
An argand diagram easily shows that z = -1 + 7i lies in the 2nd quadrant, so radians.
Last edited by mr fantastic; Jun 22nd 2008 at 04:25 PM.
Reason: Corrected a few typos