Chapter 1: Limits
Section 1.1: Naive Limits
Example 1.1.5
Obtain limx→1fx, if f is the piecewise function given by fx=2−x2x<1x−1−2⁢x3+2x≥1.
Solution
Control-drag fx=… Context Panel: Assign Function
(Click here to see a detailed explanation of how to enter a piecewise-defined function in Maple.)
fx=2−x2x<1x−1−2⁢x3+2x≥1→assign as functionf
Figure 1.1.5(a), while not essential, is extremely revealing about the behavior of fx near x=1. The jump in the function shows that the two one-sided limits will not be equal, and that the limit itself will not exist.
Code for drawing Figure 1.1.5(a) is hidden behind the cell containing it. It can also be drawn interactively via the Plot Builder. (The relevant options are: in Basic Options set the range for x, in 2-D Options select the discont option, and in Global Options set the view for axis[2].)
Figure 1.1.5(a) Graph of piecewise-defined fx
The left-hand rule in f can be obtained by simplifying f under the assumption that x<1.
Context Panel: Evaluate at a Point≻x=1
The right-hand rule in f can be obtained by simplifying f under the assumption that x≥1.
simplifyfx assuming x<1
−x2+2
→evaluate at point
1
simplifyfx assuming x≥1
x−1−2⁢x3+2
43
The limit from the left is the value of the left-hand rule taken at x=1.
The limit from the right is the value of the right-hand rule taken at x=1.
Expression palette: Limit template Obtain the limit from the left.
Expression palette: Limit template Obtain the limit from the right.
limx→1−fx = 1
limx→1+fx = 43
The limit of f as x→1
Expression palette: Limit template Obtain the limit of f.
limx→1fx = undefined
For this function, limx→1fx does not exist because the two one-sided limits do not agree. Maple reports "undefined" where the typical calculus text would use the phrase "does not exist." In other words, something like 1/0 is not defined, but a limit such as this one does not exist.
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