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

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Sec. 5]_Differentiation of Composite Functions_191<br />

and<br />

dz__dzdx ~~-~ dzdy<br />

*<br />

In all the cases considered the follow<strong>in</strong>g formula holds:<br />

. dz . . dz .<br />

dz -j- dx + 5- dy<br />

dx dy y<br />

(the <strong>in</strong>variance property of a total differential).<br />

and<br />

Example 3. F<strong>in</strong>d p<br />

^- and ^- , if<br />

du dv<br />

z=:f(x, y), where x=uv, y= .<br />

Solution. Apply<strong>in</strong>g formulas (3) and (4), we get:<br />

Example 4. Show that the function z = 2<br />

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