- Dec 11, 1999
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Calc I is a weird mix of two concepts. The first concept, limits, are fairly easy to understand, but hard to work with. They are conceptually the basis of the rest of calculus, but you don't really need to know anything about them for the rest of Calc I. Or probably II for that matter. Unless they introduce L'hopital's rule, which is just a nice, simple application of the second concept to the first.
The second concept, derivatives, is the real basis of calculus. Things you need to understand:
The second concept, derivatives, is the real basis of calculus. Things you need to understand:
- A graphed straight line has a slope. Rise over run. Easy so far. Slope is also known as "rate of change" when the X axis represents time.
- A graphed "smooth" curve of any sort has a slope at every point if you zoom in on it infinitely. (This is where limits conceptually come in.) This is also known as "instantaneous slope" or "slope of the tangent line". Jagged lines don't have slopes at their pointy bits; this will be a test question!
- A graphed curve represents a function. (You learned about those, right?) This function can be represented in algebraic form. (See also "curve fitting" if you don't believe me, but this won't be covered in Calc I.)
- Imagine finding the instantaneous slope at every point of a graphed function. (You don't have to do it; just think about it.) You can also imagine doing just a few points to approximate the goal, if I've given you too many infinities.
- Now imagine taking those slope numbers and plotting each slope number on a new graph. Plot each point at the same position on the X axis as on the original function, but on the Y axis at the slope number from the original function. You now have a new function that represents the slope of the original function at every point. This function is called the "derivative" of the original function.
- It so happens that there exist rules that will allow you to transform the algebraic form of the original function into the algebraic form of its derivative. Here they are. Memorize those, and when to apply them, and you'll be good to go. The rest is just practicing with them.