Uh, that's not a good method for life. You need to learn how to work out equations by yourself. You can't just rely on a couple of buttons and a processor.
stop trying to be the know it all mature adult
in this modern world (assuming you dont live in a third world country), a large majority of people have access to a mobile phone, 99% of mobile phones have some sort of calculation tool.
Saying you shouldn't rely on calculators is like saying you need to walk to work every day because one day your car might break down and you won't be able to use it.
We have technology, and not using it defeats the purpose of having it.
Not to mention, trying to do trig or higher level math without some form of calculation device, one problem could easily take you hours.