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

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70 Chapter 2<br />

turn around the po<strong>in</strong>t if: a) b) c)<br />

where d) where is the conjugate<br />

<strong>of</strong><br />

DEFINITION. Suppose that a cont<strong>in</strong>uous curve C with the equation<br />

does not pass through the po<strong>in</strong>t We thus say that the<br />

curve C turns times around the po<strong>in</strong>t if the curve with equation<br />

turns times around the po<strong>in</strong>t (Figure 23).<br />

FIGURE 23<br />

Consequently to def<strong>in</strong>e the number <strong>of</strong> turns <strong>of</strong> a curve around the<br />

po<strong>in</strong>t we have to look at the rotation <strong>of</strong> the vector i.e.,<br />

the vector jo<strong>in</strong><strong>in</strong>g po<strong>in</strong>ts <strong>and</strong> (cf., 221).<br />

259. How many times do the curves described <strong>in</strong> Problem 256 turn<br />

around the po<strong>in</strong>t<br />

260. Let <strong>and</strong> be the equations <strong>of</strong> two curves <strong>and</strong><br />

not pass<strong>in</strong>g through the po<strong>in</strong>t Let the variations <strong>of</strong> the argument<br />

along these curves be equal, respectively, to <strong>and</strong> What is the<br />

variation <strong>of</strong> the argument along the curve C with the equation if: a)<br />

b)

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