@misc{Smoluk_Antoni_The_2014,
 author={Smoluk, Antoni},
 identifier={DOI: 10.15611/dm.2014.11.05},
 year={2014},
 rights={Wszystkie prawa zastrzeżone (Copyright)},
 description={Didactics of Mathematics, 2014, Nr 11 (15), s. 59-64},
 publisher={Wydawnictwo Uniwersytetu Ekonomicznego we Wrocławiu},
 language={eng},
 abstract={Periodic function – this is a proposition of the new definition – has as its domainthe multiplicative group T = z  C : z = 1 of complex numbers with module one. Therefore a graph of the function f : T  R lies on the cylinder T  R, and so the graph of cosinefunction is the ellipse2212x  y .},
 type={artykuł},
 title={The graph of the cosine is an ellipse},
 keywords={domain, graph, periodic function, conditional extrema, cylinder},
}