Thanks. I got those two equations, and just noticed that I'd missed copying a negative. OK yay! I got the answer.
But yes, the solution does say "arg z = -pi/2 which is undefined ". After that it does go to say that tan(arg(z)) is undefined and solves a quadratic equation with two sets of...
z is a complex number such that z = \frac{a}{1+i} + \frac{b}{1-3i}
where a and b are real. If arg(z) = -\frac{\pi}{2} and |z|= 4, find the values of a and b.I got as far as
z = (\frac{a}{2} + \frac{b}{10}) + i(\frac{3b}{10} - \frac{a}{2})
by simplifying the original expression. Then I...