Hello DenOnde

Welcome to Math Help Forum!

Your English is excellent. It's certainly much better than my Swedish!If we writethen, using De Moivre's Theorem:We now express in polar form. On the Argand diagram it is represented by the point , so has modulus and argument . So:So:

So the values of are given by:

and its principle values (those between and ) are given by:Grandad