This open source project is an attempt to put the buttons I use most on my trusty TI-86 to work on my iPhone with a similar syntax. You can generally count on the calculator tab working, and pointing out syntax errors.
The triangle tab has issues with drawing parts of certain triangles out of the view and I don’t know how to fix that, but your input is welcome.
The Circumcircle Calculator seems to work well
Please, have fun with what I have provided.