Resizing windows is one of the most annoying interactions to perform on a computer
You have to zero in on that edge with your mouse. There's only a window of ~10 pixels so you have to try to be precise, and it seems to be a rather expensive graphical thing to show because I always see ugly, jolting artifacts, and I have a GTX 970
I'm usually using Linux, so I forget how painful this is on other systems. On Linux (and similar), you can just Alt+Middle-drag (or Alt+Right-drag, depending on Gnome vs. KDE) anywhere in the window. The closest corner will move.
Edit: I also highly recommend using mice instead of touchpads for all computer interactions. I cringe when I watch a coworker using an Apple magic touchpad, because they have to move so slowly.