With Dynamic Input turned on, all you have to do is hit the TAB key to go between the different input areas. If it is set to relative, all of the values that you type in are relative to the last point. If it is set absolute, then they are absolute to 0,0. I usually leave mine set to Polar input because I use that most often. To switch to coordinate input, I just type a comma after the first number entered and then type in the second number (and third if 3D). The first becomes the X value and the second Y.