Let http://data.artofproblemsolving.com/...1c4df4304f.gif be the graph of the parametric equations

http://data.artofproblemsolving.com/...d0ea6ee9f9.gif

What is the length of the smallest interval http://data.artofproblemsolving.com/...63c10b675d.gif such that the graph of these equations for all http://data.artofproblemsolving.com/...f9566ea488.gif produces the entire graph http://data.artofproblemsolving.com/...1c4df4304f.gif?