The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Jay Greco:
**Fear the Unit Circle No Longer!** This is the much requested FREE version of Unit Circle Helper +!One of the hardest parts of upper level math (Algebra 2+) can be memorizing the dreadful Unit Circle.Unit Circle Helper Lite is the perfect (and free!) way to learn and master the Unit Circle. With a simple tap, the values of Sin and Cos are displayed for any standard angle on the unit circle! No longer will you need to consult the internet or that crumpled up paper key when doing homework or assignments, as Unit Circle Helper Lite is quick and easy to use. Just open the beautifully designed App, swipe the screen to view the correct quadrant, and choose the angle to be displayed. It even shows degrees!**For an ad-free experience, please purchase Unit Circle Helper + for $.99! The + version also includes the values for Tan, Sec, Csc, and Cot!**