So what if you didn't pay attention in Geometry class--this is the real world, and in the real world, you have
Know it well, and you'll be on your way to discovering great new user interfaces in your apps. Do good enough of a job with that, and you may run into the greatest arithmetic problem of all: adding up all of the money you'll make with your awesome new app. Mathematical!
Here is the whole writeup; totally worth a read.