MATH 1225 Lecture Notes - Lecture 10: Asymptote, Rational Number
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Sec. 2.6 Limits at Infinity; Horizontal Asymptotes
EX: Finding horizontal asymptotes from a graph
1.
x
x
xf sin4
2.
2
1
2 x
xf
3.
xxf 1
tan
• Intuitive Definition of a Limit at Infinity: Let
f
be a function defined on some interval
,a
. Then
Lxf
x
lim
means that the values of
xf
can be made arbitrarily close to
L
by requiring
x
to be
sufficiently large.
• Intuitive Definition of a Limit at Negative Infinity: Let
f
be a function defined on some interval
a,
.
Then
Lxf
x
lim
means that the values of
xf
can be made arbitrarily close to
L
by requiring
x
to be
sufficiently large negative.
• Definition of a horizontal asymptote: The line
Ly
is called a horizontal asymptote of the curve
xfy
if either
Lxf
x
lim
or
Lxf
x
lim
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EX: Sketch the graph of
xf
and evaluate the limits
1.
xfxf
x
xf xx
lim,lim,
1
2.
xfxfexf xx
x
lim,lim,
3.
xfxfexf xx
x
lim,lim,
4.
xfxfxxf xx
lim,lim,tan 1
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Document Summary
Ex: finding horizontal asymptotes from a graph xf sin4 x x xf. Intuitive definition of a limit at infinity: let f be a function defined on some interval lim x means that the values of can be made arbitrarily close to l by requiring x to be. Intuitive definition of a limit at negative infinity: let f be a function defined on some interval . A, can be made arbitrarily close to l by requiring x to be means that the values of. Xf sufficiently large negative: definition of a horizontal asymptote: the line if either lim x. Ly is called a horizontal asymptote of the curve y . Xf lim x xf x e lim, x xf. Xf lim x xf e x lim, x xf. Xf lim x xf tan 1 x lim, x xf. If is a rational number, then lim x.