HP tech support taught me to navigate around windows with the Tab key around that time. 2 hours later we determined my motherboard was toast.

>For imaginary numbers, for instance to describe both amplitude and phase of waves.

They really drop that one on you out of left field in higher level math/science/engineering classes. One day, they are just like 'remember that imaginary number bullshit from junior high school? Here is what that is actually for.'