Consider the following parametric equation. a$.$ Eliminate the parameter to obtain an equation in x and y$.$ b$.$ Describe the curve and indicate the positive orientation. x equals negative $12$ cosine $2$ tx$=12$cos$2$t$,$ y equals negative $12$ sine $2$ ty$=12$sin$2$t$$; $0$ less than or equals t less than or equals pi$0<=$t$<=\backslash$pi