Expression 3: "r" Subscript, 0 , Baseline left parenthesis, "x" , "y" , right parenthesis equals .5 5 plus .4 5cosine left parenthesis, StartRoot, "x" squared plus "y" squared , EndRoot minus "t" , right parenthesisr0x,y=.55+.45cosx2+y2−t
3
Expression 4: "r" left parenthesis, "x" , "y" , right parenthesis equals .2 plus .8absolute value left parenthesis, "f" left parenthesis, StartFraction, arctan left parenthesis, "y" , "x" , right parenthesis Over 2 pi , EndFraction minus .1 5 StartRoot, "x" squared plus "y" squared , EndRoot plus "t" , right parenthesis , right parenthesisrx,y=.2+.8absfarctany,x2π−.15x2+y2+t