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Abel's theorem in problems and solutions - School of Mathematics

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The complex numbers 69<br />

REMARK. If a curve C is closed, i.e., then the quantity<br />

is equal to where is an <strong>in</strong>teger number.<br />

DEFINITION. If for a cont<strong>in</strong>uous closed curve C not pass<strong>in</strong>g through<br />

a po<strong>in</strong>t the variation <strong>of</strong> the argument is equal to then we say<br />

that the curve C turns times around the po<strong>in</strong>t<br />

256. How many times do the follow<strong>in</strong>g curves turn around the po<strong>in</strong>t<br />

a) (Figure 19); b)<br />

(Figure 20); c) the curve <strong>in</strong> Figure 21; d) the curve <strong>in</strong> Figure<br />

22?<br />

FIGURE 19 FIGURE 20<br />

FIGURE 21 FIGURE 22<br />

257. Prove that the number <strong>of</strong> turns <strong>of</strong> a closed cont<strong>in</strong>uous curve<br />

around the po<strong>in</strong>t does not depend on the choice <strong>of</strong> the <strong>in</strong>itial po<strong>in</strong>t,<br />

<strong>and</strong> depends only on the orientation <strong>of</strong> the curve.<br />

258. Suppose that a curve C with equation turns times around<br />

the po<strong>in</strong>t How many times does the curve with the equation

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