equations that do not graph correctly

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• Mar 19th 2009, 03:54 PM
gammaman
equations that do not graph correctly
Is there some way to know how to sketch equations that do not graph correctly on the calculator.

Stuff like your ln(something) or your e^x(something).

According to my prof, these equations do not graph correctly on the calculator, so he said we need to memorize them. Is this correct? Or is there another way?

If the first is correct, is there someplace that has the correct sketches of these type equations?
• Mar 19th 2009, 04:02 PM
e^(i*pi)
Quote:

Originally Posted by gammaman
Is there some way to know how to sketch equations that do not graph correctly on the calculator.

Stuff like your ln(something) or your e^x(something).

According to my prof, these equations do not graph correctly on the calculator, so he said we need to memorize them. Is this correct? Or is there another way?

If the first is correct, is there someplace that has the correct sketches of these type equations?

Not sure about the first part

For the second part you could probably just google image e^x or ln(x). However, when sketching you only really need to know where they cross the x axis and/or the y axis
• Mar 19th 2009, 04:07 PM
gammaman
Well that may be true, but when trying to find the area between two curves, or volume using disks and washers, it is a little more important to have as accurate a sketch as possible (since the calculator does not graph them correctly).
• Mar 19th 2009, 04:08 PM
Reckoner
Quote:

Originally Posted by gammaman
Is there some way to know how to sketch equations that do not graph correctly on the calculator.

Stuff like your ln(something) or your e^x(something).

According to my prof, these equations do not graph correctly on the calculator, so he said we need to memorize them. Is this correct? Or is there another way?

$\displaystyle \ln f(x)$ and $\displaystyle e^xg(x),$ where $\displaystyle f$ is a continuous nonnegative function and $\displaystyle g$ is continuous, should produce accurate graphs on most graphing utilities.

If you want to sketch them by hand, use the methods you learn in calculus to determine continuity, find extrema, determine where the function is increasing or decreasing, find concavity, locate inflection points, and so on, and then plot some points and sketch the graph accordingly.