For people who complain about it not being able to use offline, thats true. But then it wouldnt cost only $7 if it does offer offline calculation.
And for ones complain about too much ads. I just have one theory behind it, developers make living on apps, one way or another. Nothing is free and ideal. If you dont want ads, just pay $7 for it. $7 doesnt worth your time to write a review to complain for it.
This app offers the same feature as it does on your computer browser. Its built in keyboard is the best Ive ever used, simple looking and easy to use. I use it to solve multivariable integrals with no problems most of the time. Its also good for some trigs, and simple matrices. Or sometimes I need a quick reminder of certain properties, this is always a good app to use.
Limitation:
It wont take complex numbers. If you are a doing upper level physics, this is not going to help, at least not optics.