Complex Numbers in Expressions
Some input fields requiring a parameter expression will accept expressions that evaluate to a complex number, others will not. Input fields which accept a general global or field expressions will always accept complex numbers. This follows from the fact that they accept solution-dependence and the solution can in general be complex-valued.
To enter a complex number in an expression, use one of the imaginary unit symbols i or j. They are completely equivalent. The symbols can be used both as a built-in mathematical constant and as a postfix to a number. That is, you can write either 1+2*i or 1+2i. A parameter expression can also become complex as a result of using a complex-valued function, for example sqrt(-1) evaluates to the imaginary unit.