It's a great app, like I said I wish I had it sooner. While I already understand trig and do well in it these days, I was curious when I saw the app so I downloaded it and will now be keeping it. I was disappointed about 1 thing though, because I feel like anyone teaching trig should know this.
And this is on you Mr./Mrs. Developer, you need to rationalize the denominator when you represent values in fractions.
While tan pi/6 = 1/root3 may be correct in that it's the exact value, it is not simplified to the point where it would be correct on an exam. The correct way to represent this value is root3/3.
This is done, for those who want to learn, so that you get the square root out of the denominator which makes it easier you to do more complex calculations down the road. It is a habit that should be drilled into your education in trig.
I noticed the issue with tan, cot, sec, and csc for exact values on the unit circle. All of them have a denominator that isn't rationalized at some point on the unit circle.
Until this is fixed I will keep my review at 4 stars because while it's a great app, but it does have this error that wouldn't fly for a trig professor looking for simplified exact values.
Rationalizing square roots from the denominator is a simple process but it shouldn't be skipped for its simplicity by any means.