I need to input calculus and trigonometric notations in Android.
How to input math symbols in Android?
I know this is an old question, but the answer might help if there are still people looking for what the OP asked. There is MathKeyboard that comes loaded with math symbols from trigonometric symbols to logarithmic, integrals, subscripts, superscripts, etc.
From square roots to triple integrals, this keyboard helps you in math typing
MathKeyboard it's a keyboard that helps you with symbolic typing, for the ones who struggle to get a decent math text in common apps, this keyboard is fully compatible with all instant message services
When you open the keyboard, click on Menu to select symbols' categories.
The only caveat is that the free version contains ads.