It is easy, but only if you work hard.
I took AP Calculus AB in my sophomore year and got A's both semesters, as well as a 5 on the AP Exam. The thing with Calculus is that the concepts discussed do not go off a traditional arithmetic basis; they are more conceptual and that is where a lot of students go wrong.
Some expectations in Calc should be that you will show your work on all problems. A lot of shortcuts that you were able to take in earlier math may not be able to get you through. You will have to do all your homework, which is essentially what I am saying.
Some concepts are significantly harder than others. For instance, volumes of rotation, related rates, and optimization, tend to be hard concepts that need lots of extra practice. Simple derivatives and limits, however, will not require extra practice and could be learned just through doing homework. So make sure to plan accordingly.
No, you can't sleep through the class. You will have to work hard. But, it is not hard if you put in the right amount of effort.
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