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Problems in Mathematical Analysis.pdf - pwp.net.ipl.pt

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184_Functions of Several Variables_[Ch. 6<br />

Sec. 2. Cont<strong>in</strong>uity<br />

1. The limit of a function. A number A is called the limit of a function<br />

2 = /(*, y) as the po<strong>in</strong>t P 1<br />

(x, y) approaches the po<strong>in</strong>t P (o. ft), if for any<br />

e > there is a 6 > such that when < Q < 6, where Q = |/\x a)* + U/ 6) 1<br />

is the distance between P and P', we have the <strong>in</strong>equality<br />

I /(*, y)A\<br />

Solution. The function will be mean<strong>in</strong>gless<br />

if the denom<strong>in</strong>ator becomes<br />

zero. But ** -r/ = or y x 2 is the equation of a parabola. Hence, the given<br />

function has for its discont<strong>in</strong>uity the parabola y x 2 .<br />

1797*. F<strong>in</strong>d the follow<strong>in</strong>g limits of functions:<br />

a) li<strong>in</strong>(*?^)s<strong>in</strong>l; c)li n M; e)l<strong>in</strong>-L;<br />

1798. Test the follow<strong>in</strong>g function for cont<strong>in</strong>uity:<br />

ftx /) = / V\x* if when * 2 2<br />

-r-// 1.<br />

1799. F<strong>in</strong>d po<strong>in</strong>ts of discont<strong>in</strong>uity<br />

a) z =ln; c) e-<br />

of the functions:

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