Introduction to Calculus Refresher
The usual trouble that people have with ‘calculus’ (not counting general math phobias) is with algebra, not to mention arithmetic and other more elementary things.
Calculus itself just involves two new processes, differentiation and integration, and applications of these new things to solution of problems that would have been impossible otherwise.
Some things which were very important when calculators and computers didn’t exist are not so important now. Some things are just as important. Some things are more important. Some things are important but with a different emphasis.
At the same time, the essential ideas of much of calculus can be very well illustrated without using calculators at all! (Some not, too).
Likewise, many essential ideas of calculus can be very well illustrated without getting embroiled in awful algebra or arithmetic, not to mention trigonometry.
At the same time, study of calculus makes clear how important it is to be able to do the necessary algebra and arithmetic, whether by calculator or by hand.