18.L. Define what is meant by lim sup f = L, lim inf f : = -- ¤. %3D

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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Please help with exercise 18. L

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18.L. Define what is meant by
lim sup f = L,
lim inf f
o.
18.M. Show that if f is an upper semi-continuous function on a compact subset
K of RP with values in R, then f is bounded above and attains its supremum on K.
18.N. Show that an upper semi-continuous function on a compact set may
not be bounded below and may not attain its infimum.
18.0. Show that if A is an open subset of Rº and if f is defined on R to R by
f(x) = 1,
x E A,
0,
x ¢ A,
then f is a lower semi-continuous function. If A is a closed subset of RP, show
that f is upper semi-continuous.
18.P. Give an example of an upper semi-continuous function which has an
infinite number of points of discontinuity.
18.Q. Is it true that function on R? to R is continuous at a point if and only
if it is both upper and lower semi-continuous at this point?
Transcribed Image Text:18.L. Define what is meant by lim sup f = L, lim inf f o. 18.M. Show that if f is an upper semi-continuous function on a compact subset K of RP with values in R, then f is bounded above and attains its supremum on K. 18.N. Show that an upper semi-continuous function on a compact set may not be bounded below and may not attain its infimum. 18.0. Show that if A is an open subset of Rº and if f is defined on R to R by f(x) = 1, x E A, 0, x ¢ A, then f is a lower semi-continuous function. If A is a closed subset of RP, show that f is upper semi-continuous. 18.P. Give an example of an upper semi-continuous function which has an infinite number of points of discontinuity. 18.Q. Is it true that function on R? to R is continuous at a point if and only if it is both upper and lower semi-continuous at this point?
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