This result came up in my diff eq class the other day: If i = x^2 then x = [(sqrt(2)/2) + (sqrt(2)/2)i]^2 While there aren't a lot of use for complex numbers in this class, I still feel stupid for not knowing it. Another trick that I'd like to learn about is the "complexifying the integral" trick that was mentioned in this video: www.youtube.com/watch?v=CpM1jJ0lob8 AFAICT, some of this stuff people learned in high school.. WTF.. I don't remember anything like that in high school. What books did they use for this? I don't have enough time to read an advanced undergrad level complex analysis book. I'd just like enough knowedge of complex numbers to know what's going on. Thanks in advance.